diff --git a/.travis.yml b/.travis.yml
index 6f08335eb5..1ba3fd50a7 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -22,76 +22,59 @@ env:
         - EXTRA_PIP_FLAGS="--find-links=$EXTRA_WHEELS"
         - PRE_PIP_FLAGS="--pre $EXTRA_PIP_FLAGS --find-links $PRE_WHEELS"
 python:
-    - 3.5
     - 3.6
     - 3.7
 matrix:
   include:
-    - python: 3.4
-      dist: trusty
-      sudo: false
     # Absolute minimum dependencies
-    - python: 2.7
+    - python: 3.5
       env:
-        - DEPENDS="numpy==1.8 setuptools==30.3.0"
+        - DEPENDS="-r min-requirements.txt setuptools==30.3.0"
     # Absolute minimum dependencies
-    - python: 2.7
+    - python: 3.5
       env:
-        - DEPENDS="numpy==1.8"
+        - DEPENDS="-r min-requirements.txt"
         - CHECK_TYPE="import"
     # Absolute minimum dependencies plus oldest MPL
     # Check these against:
     # nibabel/info.py
     # doc/source/installation.rst
     # requirements.txt
-    - python: 2.7
+    - python: 3.5
       env:
-        - DEPENDS="numpy==1.8 matplotlib==1.3.1"
+        - DEPENDS="-r min-requirements.txt matplotlib==1.3.1"
     # Minimum pydicom dependency
-    - python: 2.7
+    - python: 3.5
       env:
-        - DEPENDS="numpy==1.8 pydicom==0.9.9 pillow==2.6"
+        - DEPENDS="-r min-requirements.txt pydicom==0.9.9 pillow==2.6"
     # pydicom master branch
     - python: 3.5
       env:
         - DEPENDS="numpy git+https://github.com/pydicom/pydicom.git@master"
-    # test 2.7 against pre-release builds of everything
-    - python: 2.7
-      env:
-        - EXTRA_PIP_FLAGS="$PRE_PIP_FLAGS"
     # test 3.5 against pre-release builds of everything
     - python: 3.5
       env:
         - EXTRA_PIP_FLAGS="$PRE_PIP_FLAGS"
-    - python: 2.7
+    - python: 3.5
       env:
         - INSTALL_TYPE=sdist
-    - python: 2.7
+    - python: 3.5
       env:
         - INSTALL_TYPE=wheel
-    - python: 2.7
+    - python: 3.5
       env:
         - INSTALL_TYPE=requirements
-    - python: 2.7
+    - python: 3.5
       env:
         - INSTALL_TYPE=archive
-    - python: 2.7
-      env:
-        - CHECK_TYPE="style"
     - python: 3.5
       env:
         - CHECK_TYPE="style"
     # Documentation doctests
-    - python: 2.7
-      env:
-        - CHECK_TYPE="doc_doctests"
     - python: 3.5
       env:
         - CHECK_TYPE="doc_doctests"
     # Run tests with indexed_gzip present
-    - python: 2.7
-      env:
-        - OPTIONAL_DEPENDS="indexed_gzip"
     - python: 3.5
       env:
         - OPTIONAL_DEPENDS="indexed_gzip"
diff --git a/COPYING b/COPYING
index 8511235733..aadf96e90c 100644
--- a/COPYING
+++ b/COPYING
@@ -218,34 +218,3 @@ the PDDL version 1.0 available at http://opendatacommons.org/licenses/pddl/1.0/
 
 is courtesy of the University of Massachusetts Medical School, also released
 under the PDDL.
-
-
-Six
---------------------
-
-In ``nibabel/externals/six.py``
-
-Copied from: https://pypi.python.org/packages/source/s/six/six-1.3.0.tar.gz#md5=ec47fe6070a8a64c802363d2c2b1e2ee
-
-::
-
-    Copyright (c) 2010-2013 Benjamin Peterson
-
-    Permission is hereby granted, free of charge, to any person obtaining a copy of
-    this software and associated documentation files (the "Software"), to deal in
-    the Software without restriction, including without limitation the rights to
-    use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
-    the Software, and to permit persons to whom the Software is furnished to do so,
-    subject to the following conditions:
-
-    The above copyright notice and this permission notice shall be included in all
-    copies or substantial portions of the Software.
-
-    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
-    FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
-    COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
-    IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
-    CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
-
-
diff --git a/doc/source/installation.rst b/doc/source/installation.rst
index c853de9619..2dab695e80 100644
--- a/doc/source/installation.rst
+++ b/doc/source/installation.rst
@@ -81,14 +81,10 @@ is for you.
 Requirements
 ------------
 
-.. check these against:
-    nibabel/info.py
-    requirements.txt
-    .travis.yml
-
-*  Python_ 2.7, or >= 3.4
-*  NumPy_ 1.8 or greater
-*  Six_ 1.3 or greater
+.. check these against setup.cfg
+
+*  Python_ 3.5.1 or greater
+*  NumPy_ 1.12 or greater
 *  SciPy_ (optional, for full SPM-ANALYZE support)
 *  PyDICOM_ 0.9.9 or greater (optional, for DICOM support)
 *  `Python Imaging Library`_ (optional, for PNG conversion in DICOMFS)
diff --git a/doc/source/scripts/make_coord_examples.py b/doc/source/scripts/make_coord_examples.py
index 9079cea141..f763b28c28 100644
--- a/doc/source/scripts/make_coord_examples.py
+++ b/doc/source/scripts/make_coord_examples.py
@@ -15,7 +15,6 @@
 * someones_epi.nii.gz (pretend single EPI volume)
 * someones_anatomy.nii.gz (pretend single subject structural)
 """
-from __future__ import division, print_function
 
 import math
 
diff --git a/doc/tools/build_modref_templates.py b/doc/tools/build_modref_templates.py
index 53a8be6ec4..3b988a2135 100755
--- a/doc/tools/build_modref_templates.py
+++ b/doc/tools/build_modref_templates.py
@@ -1,7 +1,6 @@
 #!/usr/bin/env python
 """Script to auto-generate our API docs.
 """
-from __future__ import print_function, division
 
 # stdlib imports
 import sys
diff --git a/min-requirements.txt b/min-requirements.txt
new file mode 100644
index 0000000000..ed4ed75bf2
--- /dev/null
+++ b/min-requirements.txt
@@ -0,0 +1,2 @@
+# Auto-generated by tools/update_requirements.py
+numpy ==1.12
diff --git a/nibabel/affines.py b/nibabel/affines.py
index 07154089a1..a7d7a4e9b8 100644
--- a/nibabel/affines.py
+++ b/nibabel/affines.py
@@ -5,7 +5,7 @@
 
 import numpy as np
 
-from six.moves import reduce
+from functools import reduce
 
 
 class AffineError(ValueError):
diff --git a/nibabel/arraywriters.py b/nibabel/arraywriters.py
index 2bd29e4ca4..fa2d1e4e1c 100644
--- a/nibabel/arraywriters.py
+++ b/nibabel/arraywriters.py
@@ -28,7 +28,6 @@ def __init__(self, array, out_dtype=None)
 something else to make sense of conversions between float and int, or between
 larger ints and smaller.
 """
-from __future__ import division, absolute_import
 
 import warnings
 
diff --git a/nibabel/benchmarks/bench_array_to_file.py b/nibabel/benchmarks/bench_array_to_file.py
index 36921a106a..4908848685 100644
--- a/nibabel/benchmarks/bench_array_to_file.py
+++ b/nibabel/benchmarks/bench_array_to_file.py
@@ -13,7 +13,6 @@
 
     nosetests -s --match '(?:^|[\\b_\\.//-])[Bb]ench' /path/to/bench_load_save.py
 """
-from __future__ import division, print_function
 
 import sys
 from io import BytesIO  # NOQA
diff --git a/nibabel/benchmarks/bench_fileslice.py b/nibabel/benchmarks/bench_fileslice.py
index b9568c65a0..764e0390b5 100644
--- a/nibabel/benchmarks/bench_fileslice.py
+++ b/nibabel/benchmarks/bench_fileslice.py
@@ -11,7 +11,6 @@
 
     nosetests -s --match '(?:^|[\\b_\\.//-])[Bb]ench' /path/to/bench_fileslice.py
 """
-from __future__ import division, print_function
 
 import sys
 from timeit import timeit
diff --git a/nibabel/benchmarks/bench_finite_range.py b/nibabel/benchmarks/bench_finite_range.py
index 5f268eb285..6aa9d9d861 100644
--- a/nibabel/benchmarks/bench_finite_range.py
+++ b/nibabel/benchmarks/bench_finite_range.py
@@ -13,7 +13,6 @@
 
     nosetests -s --match '(?:^|[\\b_\\.//-])[Bb]ench' /path/to/bench_finite_range
 """
-from __future__ import division, print_function
 
 import sys
 
diff --git a/nibabel/benchmarks/bench_load_save.py b/nibabel/benchmarks/bench_load_save.py
index c2ee68578a..59198eac1a 100644
--- a/nibabel/benchmarks/bench_load_save.py
+++ b/nibabel/benchmarks/bench_load_save.py
@@ -13,7 +13,6 @@
 
     nosetests -s --match '(?:^|[\\b_\\.//-])[Bb]ench' /path/to/bench_load_save.py
 """
-from __future__ import division, print_function
 
 import sys
 
diff --git a/nibabel/benchmarks/bench_streamlines.py b/nibabel/benchmarks/bench_streamlines.py
index c076657d27..fc1e39f8ad 100644
--- a/nibabel/benchmarks/bench_streamlines.py
+++ b/nibabel/benchmarks/bench_streamlines.py
@@ -13,11 +13,9 @@
 
     nosetests -s --match '(?:^|[\\b_\\.//-])[Bb]ench' /path/to/bench_streamlines.py
 """
-from __future__ import division, print_function
 
 import numpy as np
 
-from six.moves import zip
 from nibabel.tmpdirs import InTemporaryDirectory
 
 from numpy.testing import assert_array_equal
diff --git a/nibabel/benchmarks/butils.py b/nibabel/benchmarks/butils.py
index 36e42f270d..bea5872272 100644
--- a/nibabel/benchmarks/butils.py
+++ b/nibabel/benchmarks/butils.py
@@ -1,6 +1,5 @@
 """ Benchmarking utilities
 """
-from __future__ import print_function, division
 
 from .. import get_info
 
diff --git a/nibabel/brikhead.py b/nibabel/brikhead.py
index 1a12abfbca..49182ba705 100644
--- a/nibabel/brikhead.py
+++ b/nibabel/brikhead.py
@@ -27,14 +27,12 @@
 am aware) always be >= 1. This permits sub-brick indexing common in AFNI
 programs (e.g., example4d+orig'[0]').
 """
-from __future__ import print_function, division
 
 from copy import deepcopy
 import os
 import re
 
 import numpy as np
-from six import string_types
 
 from .arrayproxy import ArrayProxy
 from .fileslice import strided_scalar
@@ -204,7 +202,7 @@ def parse_AFNI_header(fobj):
     [1, 1, 1]
     """
     # edge case for being fed a filename instead of a file object
-    if isinstance(fobj, string_types):
+    if isinstance(fobj, str):
         with open(fobj, 'rt') as src:
             return parse_AFNI_header(src)
     # unpack variables in HEAD file
diff --git a/nibabel/checkwarns.py b/nibabel/checkwarns.py
index deb3f6f009..a5942427b6 100644
--- a/nibabel/checkwarns.py
+++ b/nibabel/checkwarns.py
@@ -8,7 +8,6 @@
 ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ##
 ''' Contexts for *with* statement allowing checks for warnings
 '''
-from __future__ import division, print_function
 
 import warnings
 
diff --git a/nibabel/cifti2/cifti2.py b/nibabel/cifti2/cifti2.py
index 104c9396cd..1a5307eba5 100644
--- a/nibabel/cifti2/cifti2.py
+++ b/nibabel/cifti2/cifti2.py
@@ -16,13 +16,8 @@
 
     http://www.nitrc.org/projects/cifti
 '''
-from __future__ import division, print_function, absolute_import
 import re
-try:
-    from collections.abc import MutableSequence, MutableMapping, Iterable
-except ImportError:
-    # PY2 compatibility
-    from collections import MutableSequence, MutableMapping, Iterable
+from collections.abc import MutableSequence, MutableMapping, Iterable
 from collections import OrderedDict
 from .. import xmlutils as xml
 from ..filebasedimages import FileBasedHeader
diff --git a/nibabel/cifti2/cifti2_axes.py b/nibabel/cifti2/cifti2_axes.py
index 30decec3d1..05ab84e6ab 100644
--- a/nibabel/cifti2/cifti2_axes.py
+++ b/nibabel/cifti2/cifti2_axes.py
@@ -120,7 +120,6 @@
 """
 import numpy as np
 from . import cifti2
-from six import string_types, add_metaclass, integer_types
 from operator import xor
 import abc
 
@@ -173,8 +172,7 @@ def to_header(axes):
     return cifti2.Cifti2Header(matrix)
 
 
-@add_metaclass(abc.ABCMeta)
-class Axis(object):
+class Axis(abc.ABC):
     """
     Abstract class for any object describing the rows or columns of a CIFTI-2 vector/matrix
 
@@ -289,7 +287,7 @@ def __init__(self, name, voxel=None, vertex=None, affine=None,
         else:
             self.vertex = np.asanyarray(vertex, dtype=int)
 
-        if isinstance(name, string_types):
+        if isinstance(name, str):
             name = [self.to_cifti_brain_structure_name(name)] * self.vertex.size
         self.name = np.asanyarray(name, dtype='U')
 
@@ -505,7 +503,7 @@ def to_cifti_brain_structure_name(name):
         """
         if name in cifti2.CIFTI_BRAIN_STRUCTURES:
             return name
-        if not isinstance(name, string_types):
+        if not isinstance(name, str):
             if len(name) == 1:
                 structure = name[0]
                 orientation = 'both'
@@ -589,7 +587,7 @@ def volume_shape(self, value):
             value = tuple(value)
             if len(value) != 3:
                 raise ValueError("Volume shape should be a tuple of length 3")
-            if not all(isinstance(v, integer_types) for v in value):
+            if not all(isinstance(v, int) for v in value):
                 raise ValueError("All elements of the volume shape should be integers")
         self._volume_shape = value
 
@@ -679,9 +677,9 @@ def __getitem__(self, item):
 
         Otherwise returns a new BrainModelAxis
         """
-        if isinstance(item, integer_types):
+        if isinstance(item, int):
             return self.get_element(item)
-        if isinstance(item, string_types):
+        if isinstance(item, str):
             raise IndexError("Can not index an Axis with a string (except for ParcelsAxis)")
         return self.__class__(self.name[item], self.voxel[item], self.vertex[item],
                               self.affine, self.volume_shape, self.nvertices)
@@ -914,7 +912,7 @@ def volume_shape(self, value):
             value = tuple(value)
             if len(value) != 3:
                 raise ValueError("Volume shape should be a tuple of length 3")
-            if not all(isinstance(v, integer_types) for v in value):
+            if not all(isinstance(v, int) for v in value):
                 raise ValueError("All elements of the volume shape should be integers")
         self._volume_shape = value
 
@@ -989,14 +987,14 @@ def __getitem__(self, item):
         - `string`: 2-element tuple of (parcel voxels, parcel vertices
         - other object that can index 1D arrays: new Parcel axis
         """
-        if isinstance(item, string_types):
+        if isinstance(item, str):
             idx = np.where(self.name == item)[0]
             if len(idx) == 0:
                 raise IndexError("Parcel %s not found" % item)
             if len(idx) > 1:
                 raise IndexError("Multiple parcels with name %s found" % item)
             return self.voxels[idx[0]], self.vertices[idx[0]]
-        if isinstance(item, integer_types):
+        if isinstance(item, int):
             return self.get_element(item)
         return self.__class__(self.name[item], self.voxels[item], self.vertices[item],
                               self.affine, self.volume_shape, self.nvertices)
@@ -1125,7 +1123,7 @@ def __add__(self, other):
         )
 
     def __getitem__(self, item):
-        if isinstance(item, integer_types):
+        if isinstance(item, int):
             return self.get_element(item)
         return self.__class__(self.name[item], self.meta[item])
 
@@ -1270,7 +1268,7 @@ def __add__(self, other):
         )
 
     def __getitem__(self, item):
-        if isinstance(item, integer_types):
+        if isinstance(item, int):
             return self.get_element(item)
         return self.__class__(self.name[item], self.label[item], self.meta[item])
 
@@ -1437,7 +1435,7 @@ def __getitem__(self, item):
                 nelements = 0
             return SeriesAxis(idx_start * self.step + self.start, self.step * step,
                               nelements, self.unit)
-        elif isinstance(item, integer_types):
+        elif isinstance(item, int):
             return self.get_element(item)
         raise IndexError('SeriesAxis can only be indexed with integers or slices '
                          'without breaking the regular structure')
diff --git a/nibabel/cifti2/parse_cifti2.py b/nibabel/cifti2/parse_cifti2.py
index 608636a446..8c3d40cd56 100644
--- a/nibabel/cifti2/parse_cifti2.py
+++ b/nibabel/cifti2/parse_cifti2.py
@@ -6,7 +6,6 @@
 #   copyright and license terms.
 #
 ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ##
-from __future__ import division, print_function, absolute_import
 
 from distutils.version import LooseVersion
 
diff --git a/nibabel/cifti2/tests/test_cifti2io_header.py b/nibabel/cifti2/tests/test_cifti2io_header.py
index e4970625a4..3e3cd9c77d 100644
--- a/nibabel/cifti2/tests/test_cifti2io_header.py
+++ b/nibabel/cifti2/tests/test_cifti2io_header.py
@@ -6,7 +6,6 @@
 #   copyright and license terms.
 #
 ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ##
-from __future__ import division, print_function, absolute_import
 
 from os.path import join as pjoin, dirname
 import io
diff --git a/nibabel/cmdline/diff.py b/nibabel/cmdline/diff.py
index 4b8b69381c..fde72431fb 100755
--- a/nibabel/cmdline/diff.py
+++ b/nibabel/cmdline/diff.py
@@ -10,7 +10,6 @@
 """
 Quick summary of the differences among a set of neuroimaging files
 """
-from __future__ import division, print_function, absolute_import
 
 import re
 import sys
diff --git a/nibabel/cmdline/ls.py b/nibabel/cmdline/ls.py
index f919700247..68bd6ee8c0 100755
--- a/nibabel/cmdline/ls.py
+++ b/nibabel/cmdline/ls.py
@@ -10,7 +10,6 @@
 """
 Output a summary table for neuroimaging files (resolution, dimensionality, etc.)
 """
-from __future__ import division, print_function, absolute_import
 
 import sys
 from optparse import OptionParser, Option
diff --git a/nibabel/cmdline/parrec2nii.py b/nibabel/cmdline/parrec2nii.py
index 9bbc303848..0dfa03cac9 100644
--- a/nibabel/cmdline/parrec2nii.py
+++ b/nibabel/cmdline/parrec2nii.py
@@ -1,6 +1,5 @@
 """Code for PAR/REC to NIfTI converter command
 """
-from __future__ import division, print_function, absolute_import
 
 from optparse import OptionParser, Option
 import numpy as np
diff --git a/nibabel/cmdline/tests/test_utils.py b/nibabel/cmdline/tests/test_utils.py
index e701925870..199eea5d41 100644
--- a/nibabel/cmdline/tests/test_utils.py
+++ b/nibabel/cmdline/tests/test_utils.py
@@ -15,7 +15,7 @@
 from os.path import (join as pjoin)
 from nibabel.testing import data_path
 from collections import OrderedDict
-from six import StringIO
+from io import StringIO
 
 
 def test_table2string():
diff --git a/nibabel/cmdline/utils.py b/nibabel/cmdline/utils.py
index e14c860274..57c0ccc286 100644
--- a/nibabel/cmdline/utils.py
+++ b/nibabel/cmdline/utils.py
@@ -18,8 +18,6 @@
 
 import numpy as np
 
-from nibabel.py3k import asunicode
-
 verbose_level = 0
 
 
@@ -100,7 +98,7 @@ def table2string(table, out=None):
             string_ += "%%%ds%%s%%%ds " \
                        % (nspacesl, nspacesr) % ('', item, '')
         string += string_.rstrip() + '\n'
-    out.write(asunicode(string))
+    out.write(string)
 
     if print2string:
         value = out.getvalue()
diff --git a/nibabel/data.py b/nibabel/data.py
index 2a53f15f64..6208ebe7d5 100644
--- a/nibabel/data.py
+++ b/nibabel/data.py
@@ -8,7 +8,7 @@
 from os.path import join as pjoin
 import glob
 import sys
-from six.moves import configparser
+import configparser
 from distutils.version import LooseVersion
 
 from .environment import get_nipy_user_dir, get_nipy_system_dir
diff --git a/nibabel/dft.py b/nibabel/dft.py
index 392856d4c1..7b39d35b81 100644
--- a/nibabel/dft.py
+++ b/nibabel/dft.py
@@ -10,7 +10,6 @@
 """ DICOM filesystem tools
 """
 
-from __future__ import division, print_function, absolute_import
 
 import os
 from os.path import join as pjoin
@@ -278,9 +277,7 @@ def __exit__(self, type, value, traceback):
 
 def _get_subdirs(base_dir, files_dict=None, followlinks=False):
     dirs = []
-    # followlinks keyword not available for python 2.5.
-    kwargs = {} if not followlinks else {'followlinks': True}
-    for (dirpath, dirnames, filenames) in os.walk(base_dir, **kwargs):
+    for (dirpath, dirnames, filenames) in os.walk(base_dir, followlinks=followlinks):
         abs_dir = os.path.realpath(dirpath)
         if abs_dir in dirs:
             raise CachingError('link cycle detected under %s' % base_dir)
diff --git a/nibabel/eulerangles.py b/nibabel/eulerangles.py
index eac1c046ed..0928cd39d3 100644
--- a/nibabel/eulerangles.py
+++ b/nibabel/eulerangles.py
@@ -85,7 +85,7 @@
 
 import math
 
-from six.moves import reduce
+from functools import reduce
 
 import numpy as np
 
diff --git a/nibabel/externals/__init__.py b/nibabel/externals/__init__.py
index 4c31772bb5..0eefb918c9 100644
--- a/nibabel/externals/__init__.py
+++ b/nibabel/externals/__init__.py
@@ -1,5 +1,2 @@
 # init for externals package
 from collections import OrderedDict
-
-from ..deprecated import ModuleProxy as _ModuleProxy
-six = _ModuleProxy('nibabel.externals.six')
diff --git a/nibabel/externals/netcdf.py b/nibabel/externals/netcdf.py
index e485533cd7..aca62aac80 100644
--- a/nibabel/externals/netcdf.py
+++ b/nibabel/externals/netcdf.py
@@ -12,7 +12,6 @@
 with NetCDF files.
 """
 
-from __future__ import division, print_function, absolute_import
 
 # TODO:
 # * properly implement ``_FillValue``.
@@ -36,13 +35,11 @@
 from mmap import mmap, ACCESS_READ
 
 import numpy as np  # noqa
-from ..py3k import asbytes, asstr
+from numpy.compat.py3k import asbytes, asstr
 from numpy import frombuffer, ndarray, dtype, empty, array, asarray
 from numpy import little_endian as LITTLE_ENDIAN
 from functools import reduce
 
-from six import integer_types
-
 
 ABSENT = b'\x00\x00\x00\x00\x00\x00\x00\x00'
 ZERO = b'\x00\x00\x00\x00'
@@ -480,8 +477,8 @@ def _write_values(self, values):
         if hasattr(values, 'dtype'):
             nc_type = REVERSE[values.dtype.char, values.dtype.itemsize]
         else:
-            types = [(t, NC_INT) for t in integer_types]
-            types += [
+            types = [
+                    (int, NC_INT),
                     (float, NC_FLOAT),
                     (str, NC_CHAR),
                     ]
diff --git a/nibabel/externals/oset.py b/nibabel/externals/oset.py
index 83b1e3e24d..0a29c661c5 100644
--- a/nibabel/externals/oset.py
+++ b/nibabel/externals/oset.py
@@ -13,13 +13,8 @@
 License: BSD-3
 """
 
-from __future__ import absolute_import
 
-try:
-    from collections.abc import MutableSet
-except ImportError:
-    # PY2 compatibility
-    from collections import MutableSet
+from collections.abc import MutableSet
 
 KEY, PREV, NEXT = range(3)
 
diff --git a/nibabel/externals/six.py b/nibabel/externals/six.py
deleted file mode 100644
index 77e656cd67..0000000000
--- a/nibabel/externals/six.py
+++ /dev/null
@@ -1,12 +0,0 @@
-""" Shim allowing some grace time for removal of six.py copy """
-# Remove around version 4.0
-from __future__ import absolute_import
-
-import warnings
-
-warnings.warn("We no longer carry a copy of the 'six' package in nibabel; "
-              "Please import the 'six' package directly",
-              FutureWarning,
-              stacklevel=2)
-
-from six import *  # noqa
diff --git a/nibabel/externals/tests/test_netcdf.py b/nibabel/externals/tests/test_netcdf.py
index 679d9d5ff4..289e6791c1 100644
--- a/nibabel/externals/tests/test_netcdf.py
+++ b/nibabel/externals/tests/test_netcdf.py
@@ -1,5 +1,4 @@
 ''' Tests for netcdf '''
-from __future__ import division, print_function, absolute_import
 
 import os
 from os.path import join as pjoin, dirname
diff --git a/nibabel/externals/tests/test_six.py b/nibabel/externals/tests/test_six.py
deleted file mode 100644
index 35db2ca851..0000000000
--- a/nibabel/externals/tests/test_six.py
+++ /dev/null
@@ -1,33 +0,0 @@
-""" Test we are deprecating externals.six import
-"""
-
-import warnings
-import types
-
-from nose.tools import assert_true, assert_equal
-
-from nibabel.deprecated import ModuleProxy
-
-
-def test_old_namespace():
-    with warnings.catch_warnings(record=True) as warns:
-        # Top level import.
-        # This import does not trigger an import of the six.py module, because
-        # it's the proxy object.
-        from nibabel.externals import six
-        assert_equal(warns, [])
-        # If there was a previous import it will be module, otherwise it will be
-        # a proxy.
-        previous_import = isinstance(six, types.ModuleType)
-        if not previous_import:
-            assert_true(isinstance(six, ModuleProxy))
-        shim_BytesIO = six.BytesIO  # just to check it works
-        # There may or may not be a warning raised on accessing the proxy,
-        # depending on whether the externals.six.py module is already imported
-        # in this test run.
-        if not previous_import:
-            assert_equal(warns.pop(0).category, FutureWarning)
-        from six import BytesIO
-        assert_equal(warns, [])
-        # The import from old module is the same as that from new
-        assert_true(shim_BytesIO is BytesIO)
diff --git a/nibabel/filebasedimages.py b/nibabel/filebasedimages.py
index c17701bc2e..64b79550e3 100644
--- a/nibabel/filebasedimages.py
+++ b/nibabel/filebasedimages.py
@@ -10,7 +10,6 @@
 
 import io
 from copy import deepcopy
-from six import string_types
 from .fileholders import FileHolder
 from .filename_parser import (types_filenames, TypesFilenamesError,
                               splitext_addext)
@@ -374,7 +373,7 @@ def make_file_map(klass, mapping=None):
         for key, ext in klass.files_types:
             file_map[key] = FileHolder()
             mapval = mapping.get(key, None)
-            if isinstance(mapval, string_types):
+            if isinstance(mapval, str):
                 file_map[key].filename = mapval
             elif hasattr(mapval, 'tell'):
                 file_map[key].fileobj = mapval
diff --git a/nibabel/fileslice.py b/nibabel/fileslice.py
index e55f48c127..af410a7e22 100644
--- a/nibabel/fileslice.py
+++ b/nibabel/fileslice.py
@@ -1,12 +1,11 @@
 """ Utilities for getting array slices out of file-like objects
 """
-from __future__ import division
 
 import operator
 from numbers import Integral
 from mmap import mmap
 
-from six.moves import reduce
+from functools import reduce
 
 import numpy as np
 
diff --git a/nibabel/fileutils.py b/nibabel/fileutils.py
index be9c214616..b88e2f7128 100644
--- a/nibabel/fileutils.py
+++ b/nibabel/fileutils.py
@@ -23,9 +23,8 @@ def read_zt_byte_strings(fobj, n_strings=1, bufsize=1024):
     Parameters
     ----------
     f : fileobj
-        File object to use.  Should implement ``read``, returning byte objects
-        (str in Python 2), and ``seek(n, 1)`` to seek from current file
-        position.
+        File object to use.  Should implement ``read``, returning byte objects,
+        and ``seek(n, 1)`` to seek from current file position.
     n_strings : int, optional
         Number of byte strings to return
     bufsize: int, optional
diff --git a/nibabel/freesurfer/io.py b/nibabel/freesurfer/io.py
index 9dda179d1c..f8d2442662 100644
--- a/nibabel/freesurfer/io.py
+++ b/nibabel/freesurfer/io.py
@@ -1,6 +1,5 @@
 """ Read / write FreeSurfer geometry, morphometry, label, annotation formats
 """
-from __future__ import division, print_function, absolute_import
 
 import warnings
 import numpy as np
@@ -8,7 +7,6 @@
 import time
 
 from collections import OrderedDict
-from six.moves import xrange
 from ..openers import Opener
 
 
@@ -357,7 +355,7 @@ def read_annot(filepath, orig_ids=False):
         to any label and orig_ids=False, its id will be set to -1.
     ctab : ndarray, shape (n_labels, 5)
         RGBT + label id colortable array.
-    names : list of str (python 2), list of bytes (python 3)
+    names : list of bytes
         The names of the labels. The length of the list is n_labels.
     """
     with open(filepath, "rb") as fobj:
@@ -432,7 +430,7 @@ def _read_annot_ctab_old_format(fobj, n_entries):
     orig_tab = orig_tab[:-1]
     names = list()
     ctab = np.zeros((n_entries, 5), dt)
-    for i in xrange(n_entries):
+    for i in range(n_entries):
         # structure name length + string
         name_length = np.fromfile(fobj, dt, 1)[0]
         name = np.fromfile(fobj, "|S%d" % name_length, 1)[0]
@@ -483,7 +481,7 @@ def _read_annot_ctab_new_format(fobj, ctab_version):
     # number of LUT entries present in the file
     entries_to_read = np.fromfile(fobj, dt, 1)[0]
     names = list()
-    for _ in xrange(entries_to_read):
+    for _ in range(entries_to_read):
         # index of this entry
         idx = np.fromfile(fobj, dt, 1)[0]
         # structure name length + string
diff --git a/nibabel/freesurfer/tests/test_io.py b/nibabel/freesurfer/tests/test_io.py
index 51fe123025..fc926ee2af 100644
--- a/nibabel/freesurfer/tests/test_io.py
+++ b/nibabel/freesurfer/tests/test_io.py
@@ -1,4 +1,3 @@
-from __future__ import division, print_function, absolute_import
 import os
 from os.path import join as pjoin, isdir
 import getpass
diff --git a/nibabel/gifti/gifti.py b/nibabel/gifti/gifti.py
index 22d6449e9a..95b0c4133a 100644
--- a/nibabel/gifti/gifti.py
+++ b/nibabel/gifti/gifti.py
@@ -11,11 +11,10 @@
 The Gifti specification was (at time of writing) available as a PDF download
 from http://www.nitrc.org/projects/gifti/
 """
-from __future__ import division, print_function, absolute_import
 
 import sys
-
 import numpy as np
+import base64
 
 from .. import xmlutils as xml
 from ..filebasedimages import SerializableImage
@@ -24,11 +23,6 @@
                    gifti_endian_codes, KIND2FMT)
 from ..deprecated import deprecate_with_version
 
-# {en,de}codestring in deprecated in Python3, but
-# {en,de}codebytes not available in Python2.
-# Therefore set the proper functions depending on the Python version.
-import base64
-
 
 class GiftiMetaData(xml.XmlSerializable):
     """ A sequence of GiftiNVPairs containing metadata for a gifti data array
diff --git a/nibabel/gifti/parse_gifti_fast.py b/nibabel/gifti/parse_gifti_fast.py
index f27e0725d6..044a70fede 100644
--- a/nibabel/gifti/parse_gifti_fast.py
+++ b/nibabel/gifti/parse_gifti_fast.py
@@ -6,7 +6,6 @@
 #   copyright and license terms.
 #
 ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ##
-from __future__ import division, print_function, absolute_import
 
 import base64
 import sys
diff --git a/nibabel/gifti/tests/test_gifti.py b/nibabel/gifti/tests/test_gifti.py
index f1285d441d..d6367b30c8 100644
--- a/nibabel/gifti/tests/test_gifti.py
+++ b/nibabel/gifti/tests/test_gifti.py
@@ -7,7 +7,6 @@
 import numpy as np
 
 import nibabel as nib
-from six import string_types
 from nibabel.gifti import (GiftiImage, GiftiDataArray, GiftiLabel,
                            GiftiLabelTable, GiftiMetaData, GiftiNVPairs,
                            GiftiCoordSystem)
@@ -176,11 +175,11 @@ def test_to_xml_open_close_deprecations():
     da = GiftiDataArray(np.ones((1,)), 'triangle')
     with clear_and_catch_warnings() as w:
         warnings.filterwarnings('always', category=DeprecationWarning)
-        assert_true(isinstance(da.to_xml_open(), string_types))
+        assert_true(isinstance(da.to_xml_open(), str))
         assert_equal(len(w), 1)
     with clear_and_catch_warnings() as w:
         warnings.filterwarnings('once', category=DeprecationWarning)
-        assert_true(isinstance(da.to_xml_close(), string_types))
+        assert_true(isinstance(da.to_xml_close(), str))
         assert_equal(len(w), 1)
 
 
diff --git a/nibabel/gifti/tests/test_parse_gifti_fast.py b/nibabel/gifti/tests/test_parse_gifti_fast.py
index 726779d988..a06180a964 100644
--- a/nibabel/gifti/tests/test_parse_gifti_fast.py
+++ b/nibabel/gifti/tests/test_parse_gifti_fast.py
@@ -6,7 +6,6 @@
 #   copyright and license terms.
 #
 ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ##
-from __future__ import division, print_function, absolute_import
 
 from os.path import join as pjoin, dirname
 import sys
diff --git a/nibabel/loadsave.py b/nibabel/loadsave.py
index 8c3041e73c..cd1efbe3d7 100644
--- a/nibabel/loadsave.py
+++ b/nibabel/loadsave.py
@@ -17,7 +17,6 @@
 from .filebasedimages import ImageFileError
 from .imageclasses import all_image_classes
 from .arrayproxy import is_proxy
-from .py3k import FileNotFoundError
 from .deprecated import deprecate_with_version
 
 
diff --git a/nibabel/mriutils.py b/nibabel/mriutils.py
index 0f27544fae..b0f3f6a86f 100644
--- a/nibabel/mriutils.py
+++ b/nibabel/mriutils.py
@@ -9,7 +9,6 @@
 """
 Utilities for calculations related to MRI
 """
-from __future__ import division
 
 __all__ = ['calculate_dwell_time']
 
diff --git a/nibabel/nicom/dicomreaders.py b/nibabel/nicom/dicomreaders.py
index d18a43af96..ad8d9c6b64 100644
--- a/nibabel/nicom/dicomreaders.py
+++ b/nibabel/nicom/dicomreaders.py
@@ -1,4 +1,3 @@
-from __future__ import division, print_function, absolute_import
 
 from os.path import join as pjoin
 import glob
diff --git a/nibabel/nicom/dicomwrappers.py b/nibabel/nicom/dicomwrappers.py
index 194227c6cf..ab80b51402 100755
--- a/nibabel/nicom/dicomwrappers.py
+++ b/nibabel/nicom/dicomwrappers.py
@@ -11,7 +11,6 @@
 processing that needs to raise an error, should be in a method, rather
 than in a property, or property-like thing.
 """
-from __future__ import division
 
 import operator
 
diff --git a/nibabel/nicom/tests/test_csareader.py b/nibabel/nicom/tests/test_csareader.py
index 592dd2ba54..a6bf589e90 100644
--- a/nibabel/nicom/tests/test_csareader.py
+++ b/nibabel/nicom/tests/test_csareader.py
@@ -130,8 +130,6 @@ def test_ice_dims():
 
 
 @dicom_test
-@skipif(sys.version_info < (2,7) and pydicom.__version__ < '1.0',
-        'Known issue for python 2.6 and pydicom < 1.0')
 def test_missing_csa_elem():
     # Test that we get None instead of raising an Exception when the file has
     # the PrivateCreator element for the CSA dict but not the element with the
diff --git a/nibabel/nicom/utils.py b/nibabel/nicom/utils.py
index 66688b801b..f1d5810775 100644
--- a/nibabel/nicom/utils.py
+++ b/nibabel/nicom/utils.py
@@ -1,8 +1,7 @@
 """ Utilities for working with DICOM datasets
 """
-from __future__ import division, print_function, absolute_import
 
-from ..py3k import asstr
+from numpy.compat.py3k import asstr
 
 
 def find_private_section(dcm_data, group_no, creator):
diff --git a/nibabel/nifti1.py b/nibabel/nifti1.py
index c2d409e81a..3979f5b96c 100644
--- a/nibabel/nifti1.py
+++ b/nibabel/nifti1.py
@@ -10,15 +10,13 @@
 
 NIfTI1 format defined at http://nifti.nimh.nih.gov/nifti-1/
 '''
-from __future__ import division, print_function
 import warnings
 from io import BytesIO
-from six import string_types
 
 import numpy as np
 import numpy.linalg as npl
+from numpy.compat.py3k import asstr
 
-from .py3k import asstr
 from .filebasedimages import SerializableImage
 from .volumeutils import Recoder, make_dt_codes, endian_codes
 from .spatialimages import HeaderDataError, ImageFileError
@@ -1390,7 +1388,7 @@ def set_intent(self, code, params=(), name='', allow_unknown=False):
         if not known_intent:
             # We can set intent via an unknown integer code, but can't via an
             # unknown string label
-            if not allow_unknown or isinstance(code, string_types):
+            if not allow_unknown or isinstance(code, str):
                 raise KeyError('Unknown intent code: ' + str(code))
         if known_intent:
             icode = intent_codes.code[code]
diff --git a/nibabel/onetime.py b/nibabel/onetime.py
index 1f410b9a1e..a036d0d229 100644
--- a/nibabel/onetime.py
+++ b/nibabel/onetime.py
@@ -19,7 +19,6 @@
 
 [2] Python data model, https://docs.python.org/reference/datamodel.html
 """
-from __future__ import division, print_function, absolute_import
 
 # -----------------------------------------------------------------------------
 # Classes and Functions
diff --git a/nibabel/openers.py b/nibabel/openers.py
index e551404561..e0706c4998 100644
--- a/nibabel/openers.py
+++ b/nibabel/openers.py
@@ -9,13 +9,8 @@
 """ Context manager openers for various fileobject types
 """
 
-import sys
-if sys.version_info[0] < 3:
-    from bz2file import BZ2File
-else:
-    from bz2 import BZ2File
+from bz2 import BZ2File
 import gzip
-import sys
 import warnings
 from os.path import splitext
 from distutils.version import StrictVersion
@@ -43,51 +38,6 @@
     HAVE_INDEXED_GZIP = False
 
 
-# The largest memory chunk that gzip can use for reads
-GZIP_MAX_READ_CHUNK = 100 * 1024 * 1024  # 100Mb
-
-
-class BufferedGzipFile(gzip.GzipFile):
-    """GzipFile able to readinto buffer >= 2**32 bytes.
-
-    This class only differs from gzip.GzipFile
-    in Python 3.5.0.
-
-    This works around a known issue in Python 3.5.
-    See https://bugs.python.org/issue25626
-    """
-
-    # This helps avoid defining readinto in Python 2.6,
-    #   where it is undefined on gzip.GzipFile.
-    # It also helps limit the exposure to this code.
-    if sys.version_info[:3] == (3, 5, 0):
-        def __init__(self, fileish, mode='rb', compresslevel=9,
-                     buffer_size=2**32 - 1):
-            super(BufferedGzipFile, self).__init__(fileish, mode=mode,
-                                                   compresslevel=compresslevel)
-            self.buffer_size = buffer_size
-
-        def readinto(self, buf):
-            """Uses self.buffer_size to do a buffered read."""
-            n_bytes = len(buf)
-            if n_bytes < 2 ** 32:
-                return super(BufferedGzipFile, self).readinto(buf)
-
-            # This works around a known issue in Python 3.5.
-            # See https://bugs.python.org/issue25626
-            mv = memoryview(buf)
-            n_read = 0
-            max_read = 2 ** 32 - 1  # Max for unsigned 32-bit integer
-            while (n_read < n_bytes):
-                n_wanted = min(n_bytes - n_read, max_read)
-                n_got = super(BufferedGzipFile, self).readinto(
-                    mv[n_read:n_read + n_wanted])
-                n_read += n_got
-                if n_got != n_wanted:
-                    break
-            return n_read
-
-
 def _gzip_open(filename, mode='rb', compresslevel=9, keep_open=False):
 
     # use indexed_gzip if possible for faster read access.  If keep_open ==
@@ -96,16 +46,9 @@ def _gzip_open(filename, mode='rb', compresslevel=9, keep_open=False):
     if HAVE_INDEXED_GZIP and mode == 'rb':
         gzip_file = IndexedGzipFile(filename, drop_handles=not keep_open)
 
-    # Fall-back to built-in GzipFile (wrapped with the BufferedGzipFile class
-    # defined above)
+    # Fall-back to built-in GzipFile
     else:
-        gzip_file = BufferedGzipFile(filename, mode, compresslevel)
-
-    # Speedup for #209, for versions of python < 3.5. Open gzip files with
-    # faster reads on large files using a larger read buffer. See
-    # https://github.com/nipy/nibabel/pull/210 for discussion
-    if hasattr(gzip_file, 'max_read_chunk'):
-        gzip_file.max_read_chunk = GZIP_MAX_READ_CHUNK
+        gzip_file = gzip.GzipFile(filename, mode, compresslevel)
 
     return gzip_file
 
diff --git a/nibabel/optpkg.py b/nibabel/optpkg.py
index fb0e00179a..d52329f186 100644
--- a/nibabel/optpkg.py
+++ b/nibabel/optpkg.py
@@ -1,7 +1,6 @@
 """ Routines to support optional packages """
 import pkgutil
 from distutils.version import LooseVersion
-from six import string_types
 from .tripwire import TripWire
 
 if pkgutil.find_loader('nose'):
@@ -12,7 +11,7 @@
 
 def _check_pkg_version(pkg, min_version):
     # Default version checking function
-    if isinstance(min_version, string_types):
+    if isinstance(min_version, str):
         min_version = LooseVersion(min_version)
     try:
         return min_version <= pkg.__version__
diff --git a/nibabel/orientations.py b/nibabel/orientations.py
index 9f3bbfed4d..ddea3159d0 100644
--- a/nibabel/orientations.py
+++ b/nibabel/orientations.py
@@ -8,7 +8,6 @@
 ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ##
 ''' Utilities for calculating and applying affine orientations '''
 
-from __future__ import division, print_function, absolute_import
 
 import numpy as np
 import numpy.linalg as npl
diff --git a/nibabel/parrec.py b/nibabel/parrec.py
index 1dfa998394..8ed9adf2c5 100644
--- a/nibabel/parrec.py
+++ b/nibabel/parrec.py
@@ -121,7 +121,6 @@
 utility via the option "--strict-sort".  The dimension info can be exported
 to a CSV file by adding the option "--volume-info".
 """
-from __future__ import print_function, division
 
 import warnings
 import numpy as np
diff --git a/nibabel/processing.py b/nibabel/processing.py
index cf9f60c76c..449e6b41fc 100644
--- a/nibabel/processing.py
+++ b/nibabel/processing.py
@@ -14,7 +14,6 @@
 
 Smoothing and resampling routines need scipy
 """
-from __future__ import print_function, division, absolute_import
 
 import numpy as np
 import numpy.linalg as npl
diff --git a/nibabel/py3k.py b/nibabel/py3k.py
index bd55158d30..02dd1f16e7 100644
--- a/nibabel/py3k.py
+++ b/nibabel/py3k.py
@@ -1,88 +1,9 @@
-"""
-Python 3 compatibility tools.
+import warnings
 
-Copied from numpy/compat/py3k.
+warnings.warn("We no longer carry a copy of the 'py3k' module in nibabel; "
+              "Please import from the 'numpy.compat.py3k' module directly. "
+              "Full removal scheduled for nibabel 4.0.",
+              FutureWarning,
+              stacklevel=2)
 
-Please prefer the routines in the six module when possible.
-
-BSD license
-"""
-
-__all__ = ['bytes', 'asbytes', 'isfileobj', 'getexception', 'strchar',
-           'unicode', 'asunicode', 'asbytes_nested', 'asunicode_nested',
-           'asstr', 'open_latin1', 'StringIO', 'BytesIO']
-
-import sys
-
-if sys.version_info[0] >= 3:
-    import io
-    StringIO = io.StringIO
-    BytesIO = io.BytesIO
-    bytes = bytes
-    unicode = str
-    asunicode = str
-
-    def asbytes(s):
-        if isinstance(s, bytes):
-            return s
-        return s.encode('latin1')
-
-    def asstr(s):
-        if isinstance(s, str):
-            return s
-        return s.decode('latin1')
-
-    def isfileobj(f):
-        return isinstance(f, io.FileIO)
-
-    def open_latin1(filename, mode='r'):
-        return open(filename, mode=mode, encoding='iso-8859-1')
-    strchar = 'U'
-    ints2bytes = lambda seq: bytes(seq)
-    ZEROB = bytes([0])
-    FileNotFoundError = FileNotFoundError
-    import builtins
-else:
-    import StringIO
-    StringIO = BytesIO = StringIO.StringIO
-    bytes = str
-    unicode = unicode
-    asbytes = str
-    asstr = str
-    strchar = 'S'
-
-    def isfileobj(f):
-        return isinstance(f, file)
-
-    def asunicode(s):
-        if isinstance(s, unicode):
-            return s
-        return s.decode('ascii')
-
-    def open_latin1(filename, mode='r'):
-        return open(filename, mode=mode)
-    ints2bytes = lambda seq: ''.join(chr(i) for i in seq)
-    ZEROB = chr(0)
-
-    class FileNotFoundError(IOError):
-        pass
-
-    import __builtin__ as builtins  # noqa
-
-
-def getexception():
-    return sys.exc_info()[1]
-
-
-def asbytes_nested(x):
-    if hasattr(x, '__iter__') and not isinstance(x, (bytes, unicode)):
-        return [asbytes_nested(y) for y in x]
-    else:
-        return asbytes(x)
-
-
-def asunicode_nested(x):
-    if hasattr(x, '__iter__') and not isinstance(x, (bytes, unicode)):
-        return [asunicode_nested(y) for y in x]
-    else:
-        return asunicode(x)
+from numpy.compat.py3k import *  # noqa
diff --git a/nibabel/rstutils.py b/nibabel/rstutils.py
index 6a330174b1..d0bdb655b0 100644
--- a/nibabel/rstutils.py
+++ b/nibabel/rstutils.py
@@ -2,7 +2,6 @@
 
 * Make ReST table given array of values
 """
-from __future__ import division
 
 import numpy as np
 
diff --git a/nibabel/streamlines/__init__.py b/nibabel/streamlines/__init__.py
index 84d810367e..7f999ca19b 100644
--- a/nibabel/streamlines/__init__.py
+++ b/nibabel/streamlines/__init__.py
@@ -2,7 +2,6 @@
 """
 import os
 import warnings
-from six import string_types
 
 from .header import Field
 from .array_sequence import ArraySequence
@@ -57,7 +56,7 @@ def detect_format(fileobj):
         except IOError:
             pass
 
-    if isinstance(fileobj, string_types):
+    if isinstance(fileobj, str):
         _, ext = os.path.splitext(fileobj)
         return FORMATS.get(ext.lower())
 
diff --git a/nibabel/streamlines/array_sequence.py b/nibabel/streamlines/array_sequence.py
index 5e6df6bf26..e86cbb5127 100644
--- a/nibabel/streamlines/array_sequence.py
+++ b/nibabel/streamlines/array_sequence.py
@@ -1,4 +1,3 @@
-from __future__ import division
 
 import numbers
 from operator import mul
diff --git a/nibabel/streamlines/tck.py b/nibabel/streamlines/tck.py
index 9b1888ebba..ffcd2e437a 100644
--- a/nibabel/streamlines/tck.py
+++ b/nibabel/streamlines/tck.py
@@ -3,15 +3,14 @@
 TCK format is defined at
 http://mrtrix.readthedocs.io/en/latest/getting_started/image_data.html?highlight=format#tracks-file-format-tck
 """
-from __future__ import division
 
 import os
 import warnings
 
 import numpy as np
+from numpy.compat.py3k import asbytes, asstr
 
 from nibabel.openers import Opener
-from nibabel.py3k import asbytes, asstr
 
 from .array_sequence import ArraySequence
 from .tractogram_file import TractogramFile
diff --git a/nibabel/streamlines/tests/test_streamlines.py b/nibabel/streamlines/tests/test_streamlines.py
index 90a18f5acf..2f96e56843 100644
--- a/nibabel/streamlines/tests/test_streamlines.py
+++ b/nibabel/streamlines/tests/test_streamlines.py
@@ -8,7 +8,7 @@
 import nibabel as nib
 from io import BytesIO
 from nibabel.tmpdirs import InTemporaryDirectory
-from nibabel.py3k import asbytes
+from numpy.compat.py3k import asbytes
 
 from nibabel.testing import data_path
 from nibabel.testing import clear_and_catch_warnings
diff --git a/nibabel/streamlines/tests/test_tractogram.py b/nibabel/streamlines/tests/test_tractogram.py
index 0fe83a26d7..888de0bd49 100644
--- a/nibabel/streamlines/tests/test_tractogram.py
+++ b/nibabel/streamlines/tests/test_tractogram.py
@@ -10,7 +10,6 @@
 from nibabel.testing import clear_and_catch_warnings
 from nose.tools import assert_equal, assert_raises, assert_true
 from numpy.testing import assert_array_equal, assert_array_almost_equal
-from six.moves import zip
 
 from .. import tractogram as module_tractogram
 from ..tractogram import is_data_dict, is_lazy_dict
diff --git a/nibabel/streamlines/tractogram.py b/nibabel/streamlines/tractogram.py
index 209ed27c26..11d72ac78a 100644
--- a/nibabel/streamlines/tractogram.py
+++ b/nibabel/streamlines/tractogram.py
@@ -2,12 +2,7 @@
 import numbers
 import numpy as np
 from warnings import warn
-
-try:
-    from collections.abc import MutableMapping
-except ImportError:
-    # PY2 compatibility
-    from collections import MutableMapping
+from collections.abc import MutableMapping
 
 from nibabel.affines import apply_affine
 
diff --git a/nibabel/streamlines/tractogram_file.py b/nibabel/streamlines/tractogram_file.py
index d422560280..f8184c8ba9 100644
--- a/nibabel/streamlines/tractogram_file.py
+++ b/nibabel/streamlines/tractogram_file.py
@@ -1,7 +1,6 @@
 """  Define abstract interface for Tractogram file classes
 """
-from abc import ABCMeta, abstractmethod
-from six import with_metaclass
+from abc import ABC, abstractmethod
 
 from .header import Field
 
@@ -34,7 +33,7 @@ def __init__(self, callable):
         super(abstractclassmethod, self).__init__(callable)
 
 
-class TractogramFile(with_metaclass(ABCMeta)):
+class TractogramFile(ABC):
     """ Convenience class to encapsulate tractogram file format. """
 
     def __init__(self, tractogram, header=None):
diff --git a/nibabel/streamlines/trk.py b/nibabel/streamlines/trk.py
index 805b44edcf..f67ab1509a 100644
--- a/nibabel/streamlines/trk.py
+++ b/nibabel/streamlines/trk.py
@@ -1,4 +1,3 @@
-from __future__ import division
 
 # Definition of trackvis header structure:
 # http://www.trackvis.org/docs/?subsect=fileformat
@@ -9,10 +8,11 @@
 import warnings
 
 import numpy as np
+from numpy.compat.py3k import asstr
+
 import nibabel as nib
 
 from nibabel.openers import Opener
-from nibabel.py3k import asstr
 from nibabel.volumeutils import (native_code, swapped_code, endian_codes)
 from nibabel.orientations import (aff2axcodes, axcodes2ornt)
 
diff --git a/nibabel/testing/__init__.py b/nibabel/testing/__init__.py
index 16f2112299..010e4d0ad1 100644
--- a/nibabel/testing/__init__.py
+++ b/nibabel/testing/__init__.py
@@ -7,7 +7,6 @@
 #
 ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ##
 ''' Utilities for testing '''
-from __future__ import division, print_function
 
 import re
 import os
@@ -30,7 +29,7 @@
 except ImportError:
     pass
 
-from six.moves import zip_longest
+from itertools import zip_longest
 
 # set path to example data
 data_path = abspath(pjoin(dirname(__file__), '..', 'tests', 'data'))
diff --git a/nibabel/tests/scriptrunner.py b/nibabel/tests/scriptrunner.py
index c5b37df80f..33b5e3dcef 100644
--- a/nibabel/tests/scriptrunner.py
+++ b/nibabel/tests/scriptrunner.py
@@ -18,22 +18,8 @@
 
 from subprocess import Popen, PIPE
 
-try:  # Python 2
-    string_types = basestring,
-except NameError:  # Python 3
-    string_types = str,
 
-
-def _get_package():
-    """ Workaround for missing ``__package__`` in Python 3.2
-    """
-    if '__package__' in globals() and not __package__ is None:
-        return __package__
-    return __name__.split('.', 1)[0]
-
-
-# Same as __package__ for Python 2.6, 2.7 and >= 3.3
-MY_PACKAGE = _get_package()
+MY_PACKAGE = __package__
 
 
 def local_script_dir(script_sdir):
@@ -112,12 +98,12 @@ def run_command(self, cmd, check_code=True):
         -------
         returncode : int
             return code from execution of `cmd`
-        stdout : bytes (python 3) or str (python 2)
+        stdout : bytes
             stdout from `cmd`
-        stderr : bytes (python 3) or str (python 2)
+        stderr : bytes
             stderr from `cmd`
         """
-        if isinstance(cmd, string_types):
+        if isinstance(cmd, str):
             cmd = [cmd]
         else:
             cmd = list(cmd)
diff --git a/nibabel/tests/test_analyze.py b/nibabel/tests/test_analyze.py
index 25ee778db9..45a4c00d62 100644
--- a/nibabel/tests/test_analyze.py
+++ b/nibabel/tests/test_analyze.py
@@ -20,7 +20,7 @@
 
 import numpy as np
 
-from six import BytesIO, StringIO
+from io import BytesIO, StringIO
 from ..spatialimages import (HeaderDataError, HeaderTypeError,
                              supported_np_types)
 from ..analyze import AnalyzeHeader, AnalyzeImage
@@ -698,8 +698,6 @@ class TestAnalyzeImage(tsi.TestSpatialImage, tsi.MmapImageMixin):
     image_class = AnalyzeImage
     can_save = True
     supported_np_types = TestAnalyzeHeader.supported_np_types
-    # Flag to skip bz2 save tests if they are going to break
-    bad_bz2 = False
 
     def test_supported_types(self):
         img = self.image_class(np.zeros((2, 3, 4)), np.eye(4))
@@ -794,9 +792,7 @@ def test_big_offset_exts(self):
         arr = np.arange(24, dtype=np.int16).reshape((2, 3, 4))
         aff = np.eye(4)
         img_ext = img_klass.files_types[0][1]
-        compressed_exts = ['', '.gz']
-        if not self.bad_bz2:
-            compressed_exts.append('.bz2')
+        compressed_exts = ['', '.gz', '.bz2']
         with InTemporaryDirectory():
             for offset in (0, 2048):
                 # Set offset in in-memory image
diff --git a/nibabel/tests/test_api_validators.py b/nibabel/tests/test_api_validators.py
index affa89d3e3..a7cbb8b555 100644
--- a/nibabel/tests/test_api_validators.py
+++ b/nibabel/tests/test_api_validators.py
@@ -1,8 +1,5 @@
 """ Metaclass and class for validating instance APIs
 """
-from __future__ import division, print_function, absolute_import
-
-from six import with_metaclass
 
 from nose.tools import assert_equal
 
@@ -33,7 +30,7 @@ def meth(self):
         return klass
 
 
-class ValidateAPI(with_metaclass(validator2test)):
+class ValidateAPI(metaclass=validator2test):
     """ A class to validate APIs
 
     Your job is twofold:
diff --git a/nibabel/tests/test_arrayproxy.py b/nibabel/tests/test_arrayproxy.py
index 187d5940df..b1cc081b6d 100644
--- a/nibabel/tests/test_arrayproxy.py
+++ b/nibabel/tests/test_arrayproxy.py
@@ -8,7 +8,6 @@
 ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ##
 """ Tests for arrayproxy module
 """
-from __future__ import division, print_function, absolute_import
 
 import warnings
 import gzip
diff --git a/nibabel/tests/test_arraywriters.py b/nibabel/tests/test_arraywriters.py
index b4a3a48e93..d5547e875f 100644
--- a/nibabel/tests/test_arraywriters.py
+++ b/nibabel/tests/test_arraywriters.py
@@ -2,11 +2,8 @@
 
 See docstring of :mod:`nibabel.arraywriters` for API.
 """
-from __future__ import division, print_function, absolute_import
 
-import sys
 from platform import python_compiler, machine
-from distutils.version import LooseVersion
 import itertools
 import numpy as np
 
@@ -34,8 +31,6 @@
 IUINT_TYPES = INT_TYPES + UINT_TYPES
 NUMERIC_TYPES = CFLOAT_TYPES + IUINT_TYPES
 
-NP_VERSION = LooseVersion(np.__version__)
-
 
 def round_trip(writer, order='F', apply_scale=True):
     sio = BytesIO()
@@ -66,29 +61,14 @@ def test_arraywriters():
             assert_array_equal(arr, round_trip(aw))
             # Byteswapped should be OK
             bs_arr = arr.byteswap().newbyteorder('S')
-            # Except on some numpies for complex256, where the array does not
-            # equal itself
-            if not np.all(bs_arr == arr):
-                assert_true(NP_VERSION <= LooseVersion('1.7.0'))
-                assert_true(on_powerpc())
-                assert_true(type == np.complex256)
-            else:
-                bs_aw = klass(bs_arr)
-                bs_aw_rt = round_trip(bs_aw)
-                # On Ubuntu 13.04 with python 3.3 __eq__ comparison on
-                # arrays with complex numbers fails here for some
-                # reason -- not our fault, and to test correct operation we
-                # will just compare element by element
-                if NP_VERSION == '1.7.1' and sys.version_info[:2] == (3, 3):
-                    assert_array_equal_ = lambda x, y: np.all([x_ == y_ for x_, y_ in zip(x, y)])
-                else:
-                    assert_array_equal_ = assert_array_equal
-                # assert against original array because POWER7 was running into
-                # trouble using the byteswapped array (bs_arr)
-                assert_array_equal_(arr, bs_aw_rt)
-                bs_aw2 = klass(bs_arr, arr.dtype)
-                bs_aw2_rt = round_trip(bs_aw2)
-                assert_array_equal(arr, bs_aw2_rt)
+            bs_aw = klass(bs_arr)
+            bs_aw_rt = round_trip(bs_aw)
+            # assert against original array because POWER7 was running into
+            # trouble using the byteswapped array (bs_arr)
+            assert_array_equal(arr, bs_aw_rt)
+            bs_aw2 = klass(bs_arr, arr.dtype)
+            bs_aw2_rt = round_trip(bs_aw2)
+            assert_array_equal(arr, bs_aw2_rt)
             # 2D array
             arr2 = np.reshape(arr, (2, 5))
             a2w = klass(arr2)
diff --git a/nibabel/tests/test_batteryrunners.py b/nibabel/tests/test_batteryrunners.py
index 71cbbba072..1130c2f4cb 100644
--- a/nibabel/tests/test_batteryrunners.py
+++ b/nibabel/tests/test_batteryrunners.py
@@ -9,7 +9,7 @@
 ''' Tests for BatteryRunner and Report objects
 '''
 
-from six import StringIO
+from io import StringIO
 
 import logging
 
diff --git a/nibabel/tests/test_brikhead.py b/nibabel/tests/test_brikhead.py
index c1632c06c2..a99e6c41b6 100644
--- a/nibabel/tests/test_brikhead.py
+++ b/nibabel/tests/test_brikhead.py
@@ -6,7 +6,6 @@
 #   copyright and license terms.
 #
 ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ##
-from __future__ import division, print_function, absolute_import
 
 from os.path import join as pjoin
 
diff --git a/nibabel/tests/test_data.py b/nibabel/tests/test_data.py
index fbb225838d..641d6e55cd 100644
--- a/nibabel/tests/test_data.py
+++ b/nibabel/tests/test_data.py
@@ -1,7 +1,6 @@
 # emacs: -*- mode: python; py-indent-offset: 4; indent-tabs-mode: nil -*-
 # vi: set ft=python sts=4 ts=4 sw=4 et:
 ''' Tests for data module '''
-from __future__ import division, print_function, absolute_import
 import os
 from os.path import join as pjoin
 from os import environ as env
diff --git a/nibabel/tests/test_diff.py b/nibabel/tests/test_diff.py
index 4f99ca145f..754779dbc9 100644
--- a/nibabel/tests/test_diff.py
+++ b/nibabel/tests/test_diff.py
@@ -2,7 +2,6 @@
 # vi: set ft=python sts=4 ts=4 sw=4 et:
 """ Test diff
 """
-from __future__ import division, print_function, absolute_import
 
 from os.path import (dirname, join as pjoin, abspath)
 import numpy as np
diff --git a/nibabel/tests/test_ecat.py b/nibabel/tests/test_ecat.py
index 2bfd983c53..9005d32d4f 100644
--- a/nibabel/tests/test_ecat.py
+++ b/nibabel/tests/test_ecat.py
@@ -6,7 +6,6 @@
 #   copyright and license terms.
 #
 ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ##
-from __future__ import division, print_function, absolute_import
 
 import os
 import warnings
diff --git a/nibabel/tests/test_ecat_data.py b/nibabel/tests/test_ecat_data.py
index dce96646e8..471bc6b93c 100644
--- a/nibabel/tests/test_ecat_data.py
+++ b/nibabel/tests/test_ecat_data.py
@@ -8,7 +8,6 @@
 ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ##
 """ Test we can correctly import example ECAT files
 """
-from __future__ import print_function, absolute_import
 
 import os
 from os.path import join as pjoin
diff --git a/nibabel/tests/test_filehandles.py b/nibabel/tests/test_filehandles.py
index 365a418890..1533b7c4f8 100644
--- a/nibabel/tests/test_filehandles.py
+++ b/nibabel/tests/test_filehandles.py
@@ -1,7 +1,6 @@
 """
 Check that loading an image does not use up filehandles.
 """
-from __future__ import division, print_function, absolute_import
 
 from os.path import join as pjoin
 import shutil
diff --git a/nibabel/tests/test_fileslice.py b/nibabel/tests/test_fileslice.py
index e9cfe8e0a4..19735200eb 100644
--- a/nibabel/tests/test_fileslice.py
+++ b/nibabel/tests/test_fileslice.py
@@ -2,8 +2,6 @@
 
 import sys
 
-PY2 = sys.version_info[0] < 3
-
 from io import BytesIO
 from itertools import product
 from functools import partial
@@ -13,9 +11,6 @@
 
 import numpy as np
 
-# np > 1.11 makes double ellipsis illegal in indices
-HAVE_NP_GT_1p11 = LooseVersion(np.__version__) > '1.11'
-
 from ..fileslice import (is_fancy, canonical_slicers, fileslice,
                          predict_shape, read_segments, _positive_slice,
                          threshold_heuristic, optimize_slicer, slice2len,
@@ -48,7 +43,7 @@ def test_is_fancy():
         _check_slice(slice0)
         _check_slice((slice0,))  # tuple is same
         # Double ellipsis illegal in np 1.12dev - set up check for that case
-        maybe_bad = HAVE_NP_GT_1p11 and slice0 is Ellipsis
+        maybe_bad = slice0 is Ellipsis
         for slice1 in slices:
             if maybe_bad and slice1 is Ellipsis:
                 continue
@@ -250,9 +245,6 @@ def test_threshold_heuristic():
     assert_equal(threshold_heuristic(1, 9, 1, skip_thresh=7), None)
     assert_equal(threshold_heuristic(1, 9, 2, skip_thresh=16), 'full')
     assert_equal(threshold_heuristic(1, 9, 2, skip_thresh=15), None)
-    # long if on Python 2
-    if PY2:
-        assert_equal(threshold_heuristic(long(1), 9, 1, skip_thresh=8), 'full')
     # full slice, smallest step size
     assert_equal(threshold_heuristic(
         slice(0, 9, 1), 9, 2, skip_thresh=2),
@@ -515,10 +507,6 @@ def test_optimize_read_slicers():
     assert_equal(optimize_read_slicers(
         (1, 2, 3), (2, 3, 4), 4, _always),
         ((sn, sn, 3), (1, 2)))
-    if PY2:  # Check we can pass in longs as well
-        assert_equal(optimize_read_slicers(
-            (long(1), long(2), long(3)), (2, 3, 4), 4, _always),
-            ((sn, sn, 3), (1, 2)))
 
 
 def test_slicers2segments():
@@ -540,10 +528,6 @@ def test_slicers2segments():
     assert_equal(slicers2segments(
         (slice(None), slice(None), 2), (10, 6, 4), 7, 4),
         [[7 + 10 * 6 * 2 * 4, 10 * 6 * 4]])
-    if PY2:  # Check we can pass longs on Python 2
-        assert_equal(
-            slicers2segments((long(0), long(1), long(2)), (10, 6, 4), 7, 4),
-            [[7 + 10 * 4 + 10 * 6 * 2 * 4, 4]])
 
 
 def test_calc_slicedefs():
diff --git a/nibabel/tests/test_floating.py b/nibabel/tests/test_floating.py
index 96376270b1..d9401db156 100644
--- a/nibabel/tests/test_floating.py
+++ b/nibabel/tests/test_floating.py
@@ -2,8 +2,6 @@
 """
 import sys
 
-PY2 = sys.version_info[0] < 3
-
 from distutils.version import LooseVersion
 
 import numpy as np
@@ -110,9 +108,7 @@ def test_check_nmant_nexp():
             assert_true(_check_nmant(t, ti['nmant']))
         # Test fails for longdouble after blacklisting of OSX powl as of numpy
         # 1.12 - see https://github.com/numpy/numpy/issues/8307
-        if (t != np.longdouble or
-              sys.platform != 'darwin' or
-              LooseVersion(np.__version__) < LooseVersion('1.12')):
+        if t != np.longdouble or sys.platform != 'darwin':
             assert_true(_check_maxexp(t, ti['maxexp']))
 
 
@@ -186,11 +182,6 @@ def test_int_to_float():
     i = 2**(nmant + 1) - 1
     assert_equal(as_int(int_to_float(i, LD)), i)
     assert_equal(as_int(int_to_float(-i, LD)), -i)
-    # Test no error for longs
-    if PY2:
-        i = long(i)
-        assert_equal(as_int(int_to_float(i, LD)), i)
-        assert_equal(as_int(int_to_float(-i, LD)), -i)
     # If longdouble can cope with 2**64, test
     if nmant >= 63:
         # Check conversion to int; the line below causes an error subtracting
diff --git a/nibabel/tests/test_funcs.py b/nibabel/tests/test_funcs.py
index 6032c08672..8a2a7918d8 100644
--- a/nibabel/tests/test_funcs.py
+++ b/nibabel/tests/test_funcs.py
@@ -7,7 +7,6 @@
 #
 ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ##
 ''' Test for image funcs '''
-from __future__ import division, print_function, absolute_import
 
 import numpy as np
 
diff --git a/nibabel/tests/test_helpers.py b/nibabel/tests/test_helpers.py
index 7b05a4d666..928b4bd1a3 100644
--- a/nibabel/tests/test_helpers.py
+++ b/nibabel/tests/test_helpers.py
@@ -31,33 +31,6 @@ def bytesio_round_trip(img):
     return klass.from_file_map(bytes_map)
 
 
-def bz2_mio_error():
-    """ Return True if writing mat 4 file fails
-
-    Writing an empty string can fail for bz2 objects in python 3.3:
-
-    https://bugs.python.org/issue16828
-
-    This in turn causes scipy to give this error when trying to write bz2 mat
-    files.
-
-    This won't cause a problem for scipy releases after Jan 24 2014 because of
-    commit 98ef522d99 (in scipy)
-    """
-    if not have_scipy:
-        return True
-    import scipy.io
-
-    with InTemporaryDirectory():
-        with ImageOpener('test.mat.bz2', 'wb') as fobj:
-            try:
-                scipy.io.savemat(fobj, {'a': 1}, format='4')
-            except ValueError:
-                return True
-            else:
-                return False
-
-
 def assert_data_similar(arr, params):
     """ Check data is the same if recorded, otherwise check summaries
 
diff --git a/nibabel/tests/test_image_api.py b/nibabel/tests/test_image_api.py
index ac2a2428c4..979b8777f9 100644
--- a/nibabel/tests/test_image_api.py
+++ b/nibabel/tests/test_image_api.py
@@ -23,12 +23,10 @@
 * ``img.in_memory`` is True for an array image, and for a proxy image that is
   cached, but False otherwise.
 """
-from __future__ import division, print_function, absolute_import
 
 import warnings
 from functools import partial
 from itertools import product
-from six import string_types
 
 import numpy as np
 
@@ -578,7 +576,7 @@ def validate_path_maybe_image(self, imaker, params):
             assert_true(isinstance(test, bool))
             if sniff is not None:
                 assert isinstance(sniff[0], bytes)
-                assert isinstance(sniff[1], string_types)
+                assert isinstance(sniff[1], str)
 
 
 class MakeImageAPI(LoadImageAPI):
diff --git a/nibabel/tests/test_image_load_save.py b/nibabel/tests/test_image_load_save.py
index f7318945e7..7101b6a31b 100644
--- a/nibabel/tests/test_image_load_save.py
+++ b/nibabel/tests/test_image_load_save.py
@@ -7,7 +7,6 @@
 #
 ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ##
 ''' Tests for loader function '''
-from __future__ import division, print_function, absolute_import
 from io import BytesIO
 
 import shutil
diff --git a/nibabel/tests/test_image_types.py b/nibabel/tests/test_image_types.py
index e72ad6bbbc..3ffc65eead 100644
--- a/nibabel/tests/test_image_types.py
+++ b/nibabel/tests/test_image_types.py
@@ -7,7 +7,6 @@
 #
 ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ##
 ''' Tests for is_image / may_contain_header functions '''
-from __future__ import division, print_function, absolute_import
 
 import copy
 from os.path import dirname, basename, join as pjoin
diff --git a/nibabel/tests/test_loadsave.py b/nibabel/tests/test_loadsave.py
index 676c09c121..4c1c703389 100644
--- a/nibabel/tests/test_loadsave.py
+++ b/nibabel/tests/test_loadsave.py
@@ -1,6 +1,5 @@
 """ Testing loadsave module
 """
-from __future__ import print_function
 
 from os.path import dirname, join as pjoin
 import shutil
@@ -22,7 +21,6 @@
 
 from nose.tools import (assert_true, assert_false, assert_raises,
                         assert_equal, assert_not_equal)
-from ..py3k import FileNotFoundError
 
 data_path = pjoin(dirname(__file__), 'data')
 
diff --git a/nibabel/tests/test_minc1.py b/nibabel/tests/test_minc1.py
index 1c150b02d5..50f4955917 100644
--- a/nibabel/tests/test_minc1.py
+++ b/nibabel/tests/test_minc1.py
@@ -6,7 +6,6 @@
 #   copyright and license terms.
 #
 ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ##
-from __future__ import division, print_function, absolute_import
 
 from os.path import join as pjoin
 
diff --git a/nibabel/tests/test_minc2.py b/nibabel/tests/test_minc2.py
index c4cb9341ca..d456de0eec 100644
--- a/nibabel/tests/test_minc2.py
+++ b/nibabel/tests/test_minc2.py
@@ -6,7 +6,6 @@
 #   copyright and license terms.
 #
 ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ##
-from __future__ import division, print_function, absolute_import
 
 from os.path import join as pjoin
 
diff --git a/nibabel/tests/test_minc2_data.py b/nibabel/tests/test_minc2_data.py
index 1ec4999a43..0471f87e7e 100644
--- a/nibabel/tests/test_minc2_data.py
+++ b/nibabel/tests/test_minc2_data.py
@@ -8,7 +8,6 @@
 ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ##
 """ Test we can correctly import example MINC2_PATH files
 """
-from __future__ import print_function, absolute_import
 
 import os
 from os.path import join as pjoin
diff --git a/nibabel/tests/test_mriutils.py b/nibabel/tests/test_mriutils.py
index 6978d9c253..527afc61ba 100644
--- a/nibabel/tests/test_mriutils.py
+++ b/nibabel/tests/test_mriutils.py
@@ -8,7 +8,6 @@
 ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ##
 """ Testing mriutils module
 """
-from __future__ import division
 
 
 from numpy.testing import (assert_almost_equal,
diff --git a/nibabel/tests/test_nifti1.py b/nibabel/tests/test_nifti1.py
index 931455e75a..38863e9aa2 100644
--- a/nibabel/tests/test_nifti1.py
+++ b/nibabel/tests/test_nifti1.py
@@ -7,13 +7,10 @@
 #
 ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ##
 ''' Tests for nifti reading package '''
-from __future__ import division, print_function, absolute_import
 import os
 import warnings
 import struct
 
-import six
-
 import numpy as np
 
 from nibabel import nifti1 as nifti1
@@ -943,16 +940,16 @@ def test_set_sform(self):
     def test_sqform_code_type(self):
         # make sure get_s/qform returns codes as integers
         img = self.image_class(np.zeros((2, 3, 4)), None)
-        assert isinstance(img.get_sform(coded=True)[1], six.integer_types)
-        assert isinstance(img.get_qform(coded=True)[1], six.integer_types)
+        assert isinstance(img.get_sform(coded=True)[1], int)
+        assert isinstance(img.get_qform(coded=True)[1], int)
         img.set_sform(None, 3)
         img.set_qform(None, 3)
-        assert isinstance(img.get_sform(coded=True)[1], six.integer_types)
-        assert isinstance(img.get_qform(coded=True)[1], six.integer_types)
+        assert isinstance(img.get_sform(coded=True)[1], int)
+        assert isinstance(img.get_qform(coded=True)[1], int)
         img.set_sform(None, 2.0)
         img.set_qform(None, 4.0)
-        assert isinstance(img.get_sform(coded=True)[1], six.integer_types)
-        assert isinstance(img.get_qform(coded=True)[1], six.integer_types)
+        assert isinstance(img.get_sform(coded=True)[1], int)
+        assert isinstance(img.get_qform(coded=True)[1], int)
         img.set_sform(None, img.get_sform(coded=True)[1])
         img.set_qform(None, img.get_qform(coded=True)[1])
 
diff --git a/nibabel/tests/test_nifti2.py b/nibabel/tests/test_nifti2.py
index 8c7afd9ea4..730e30a689 100644
--- a/nibabel/tests/test_nifti2.py
+++ b/nibabel/tests/test_nifti2.py
@@ -7,7 +7,6 @@
 #
 ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ##
 ''' Tests for nifti2 reading package '''
-from __future__ import division, print_function, absolute_import
 import os
 
 import numpy as np
diff --git a/nibabel/tests/test_openers.py b/nibabel/tests/test_openers.py
index 6aeb66aaf7..69704eaeb1 100644
--- a/nibabel/tests/test_openers.py
+++ b/nibabel/tests/test_openers.py
@@ -13,7 +13,7 @@
 from io import BytesIO, UnsupportedOperation
 from distutils.version import StrictVersion
 
-from ..py3k import asstr, asbytes
+from numpy.compat.py3k import asstr, asbytes
 from ..openers import Opener, ImageOpener, HAVE_INDEXED_GZIP, BZ2File
 from ..tmpdirs import InTemporaryDirectory
 from ..volumeutils import BinOpener
diff --git a/nibabel/tests/test_optpkg.py b/nibabel/tests/test_optpkg.py
index c0930e848a..99f90b5de6 100644
--- a/nibabel/tests/test_optpkg.py
+++ b/nibabel/tests/test_optpkg.py
@@ -4,6 +4,7 @@
 import mock
 import types
 import sys
+import builtins
 from distutils.version import LooseVersion
 
 from nose import SkipTest
@@ -11,7 +12,6 @@
                         assert_equal)
 
 
-from nibabel.py3k import builtins
 from nibabel.optpkg import optional_package
 from nibabel.tripwire import TripWire, TripWireError
 
diff --git a/nibabel/tests/test_parrec_data.py b/nibabel/tests/test_parrec_data.py
index 630e66cab8..1cbd2923e9 100644
--- a/nibabel/tests/test_parrec_data.py
+++ b/nibabel/tests/test_parrec_data.py
@@ -1,6 +1,5 @@
 """ Test we can correctly import example PARREC files
 """
-from __future__ import print_function, absolute_import
 
 from glob import glob
 from os.path import join as pjoin, basename, splitext, exists
diff --git a/nibabel/tests/test_processing.py b/nibabel/tests/test_processing.py
index 34b30f14c8..a09bd4cd85 100644
--- a/nibabel/tests/test_processing.py
+++ b/nibabel/tests/test_processing.py
@@ -8,7 +8,6 @@
 ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ##
 """ Testing processing module
 """
-from __future__ import division, print_function
 
 from os.path import dirname, join as pjoin
 
diff --git a/nibabel/tests/test_proxy_api.py b/nibabel/tests/test_proxy_api.py
index 7280c5552d..f1a1248c61 100644
--- a/nibabel/tests/test_proxy_api.py
+++ b/nibabel/tests/test_proxy_api.py
@@ -27,7 +27,6 @@
 
 These last are to allow the proxy to be re-used with different images.
 """
-from __future__ import division, print_function, absolute_import
 
 from os.path import join as pjoin
 import warnings
@@ -36,7 +35,6 @@
 
 import numpy as np
 
-from six import string_types
 from ..volumeutils import apply_read_scaling
 from ..analyze import AnalyzeHeader
 from ..spm99analyze import Spm99AnalyzeHeader
@@ -153,7 +151,7 @@ def validate_header_isolated(self, pmaker, params):
     def validate_fileobj_isolated(self, pmaker, params):
         # Check file position of read independent of file-like object
         prox, fio, hdr = pmaker()
-        if isinstance(fio, string_types):
+        if isinstance(fio, str):
             return
         assert_array_equal(prox, params['arr_out'])
         fio.read()  # move to end of file
diff --git a/nibabel/tests/test_rstutils.py b/nibabel/tests/test_rstutils.py
index 9fd708ba64..51103c45ca 100644
--- a/nibabel/tests/test_rstutils.py
+++ b/nibabel/tests/test_rstutils.py
@@ -1,13 +1,10 @@
 """ Test printable table
 """
-from __future__ import division, print_function
 
-import sys
 import numpy as np
 
 from ..rstutils import rst_table
 
-from nose import SkipTest
 from nose.tools import assert_equal, assert_raises
 
 
@@ -15,9 +12,6 @@ def test_rst_table():
     # Tests for printable table function
     R, C = 3, 4
     cell_values = np.arange(R * C).reshape((R, C))
-    if (sys.version_info[:3] == (3, 2, 3) and np.__version__ == '1.6.1'):
-        raise SkipTest("Known (later fixed) bug in python3.2/numpy "
-                       "treating np.int64 as str")
     assert_equal(rst_table(cell_values),
                  """+--------+--------+--------+--------+--------+
 |        | col[0] | col[1] | col[2] | col[3] |
diff --git a/nibabel/tests/test_scaling.py b/nibabel/tests/test_scaling.py
index d318c9f810..019cc58d1c 100644
--- a/nibabel/tests/test_scaling.py
+++ b/nibabel/tests/test_scaling.py
@@ -7,7 +7,6 @@
 #
 ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ##
 ''' Test for scaling / rounding in volumeutils module '''
-from __future__ import division, print_function, absolute_import
 
 import numpy as np
 
diff --git a/nibabel/tests/test_scripts.py b/nibabel/tests/test_scripts.py
index 2c17c33fd1..99e9c546f0 100644
--- a/nibabel/tests/test_scripts.py
+++ b/nibabel/tests/test_scripts.py
@@ -4,7 +4,6 @@
 
 Test running scripts
 """
-from __future__ import division, print_function, absolute_import
 
 import sys
 import os
diff --git a/nibabel/tests/test_spm99analyze.py b/nibabel/tests/test_spm99analyze.py
index 5ee94e98c2..137d3b0451 100644
--- a/nibabel/tests/test_spm99analyze.py
+++ b/nibabel/tests/test_spm99analyze.py
@@ -31,7 +31,7 @@
 from ..testing import assert_allclose_safely, suppress_warnings
 
 from . import test_analyze
-from .test_helpers import (bytesio_round_trip, bytesio_filemap, bz2_mio_error)
+from .test_helpers import bytesio_round_trip, bytesio_filemap
 
 FLOAT_TYPES = np.sctypes['float']
 COMPLEX_TYPES = np.sctypes['complex']
@@ -404,8 +404,6 @@ def test_nan2zero_range_ok(self):
 class TestSpm99AnalyzeImage(test_analyze.TestAnalyzeImage, ImageScalingMixin):
     # class for testing images
     image_class = Spm99AnalyzeImage
-    # Flag to skip bz2 save tests if they are going to break
-    bad_bz2 = bz2_mio_error()
 
     # Decorating the old way, before the team invented @
     test_data_hdr_cache = (scipy_skip(
diff --git a/nibabel/tests/test_testing.py b/nibabel/tests/test_testing.py
index 40d5ebc41e..f770ac4b0e 100644
--- a/nibabel/tests/test_testing.py
+++ b/nibabel/tests/test_testing.py
@@ -1,6 +1,5 @@
 """ Tests for warnings context managers
 """
-from __future__ import division, print_function, absolute_import
 
 import sys
 import warnings
@@ -14,18 +13,6 @@
                        get_fresh_mod, assert_re_in)
 
 
-def assert_warn_len_equal(mod, n_in_context):
-    mod_warns = mod.__warningregistry__
-    # Python 3.4 appears to clear any pre-existing warnings of the same type,
-    # when raising warnings inside a catch_warnings block. So, there is a
-    # warning generated by the tests within the context manager, but no
-    # previous warnings.
-    if 'version' in mod_warns:
-        assert_equal(len(mod_warns), 2)  # including 'version'
-    else:
-        assert_equal(len(mod_warns), n_in_context)
-
-
 def test_assert_allclose_safely():
     # Test the safe version of allclose
     assert_allclose_safely([1, 1], [1, 1])
diff --git a/nibabel/tests/test_tmpdirs.py b/nibabel/tests/test_tmpdirs.py
index 48fa5885a9..1d35b59269 100644
--- a/nibabel/tests/test_tmpdirs.py
+++ b/nibabel/tests/test_tmpdirs.py
@@ -1,5 +1,4 @@
 """ Test tmpdirs module """
-from __future__ import division, print_function, absolute_import
 
 from os import getcwd
 from os.path import realpath, abspath, dirname, isfile
diff --git a/nibabel/tests/test_trackvis.py b/nibabel/tests/test_trackvis.py
index 96f96a3f44..076e22f74e 100644
--- a/nibabel/tests/test_trackvis.py
+++ b/nibabel/tests/test_trackvis.py
@@ -1,5 +1,4 @@
 ''' Testing trackvis module '''
-from __future__ import division, print_function, absolute_import
 
 from functools import partial
 
diff --git a/nibabel/tests/test_volumeutils.py b/nibabel/tests/test_volumeutils.py
index fcdc5c2713..6eeb6c6e55 100644
--- a/nibabel/tests/test_volumeutils.py
+++ b/nibabel/tests/test_volumeutils.py
@@ -7,7 +7,6 @@
 #
 ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ##
 ''' Test for volumeutils module '''
-from __future__ import division
 
 import os
 from os.path import exists
diff --git a/nibabel/tests/test_wrapstruct.py b/nibabel/tests/test_wrapstruct.py
index 5e307067ab..45e8c28a52 100644
--- a/nibabel/tests/test_wrapstruct.py
+++ b/nibabel/tests/test_wrapstruct.py
@@ -26,8 +26,7 @@
 import logging
 import numpy as np
 
-from io import BytesIO
-from six import StringIO
+from io import BytesIO, StringIO
 from ..wrapstruct import WrapStructError, WrapStruct, LabeledWrapStruct
 from ..batteryrunners import Report
 
diff --git a/nibabel/tmpdirs.py b/nibabel/tmpdirs.py
index 8c1b704260..2636d8acb7 100644
--- a/nibabel/tmpdirs.py
+++ b/nibabel/tmpdirs.py
@@ -8,7 +8,6 @@
 ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ##
 ''' Contexts for *with* statement providing temporary directories
 '''
-from __future__ import division, print_function, absolute_import
 import os
 import shutil
 from tempfile import template, mkdtemp
diff --git a/nibabel/trackvis.py b/nibabel/trackvis.py
index 233e10ba79..691ad7b537 100644
--- a/nibabel/trackvis.py
+++ b/nibabel/trackvis.py
@@ -4,26 +4,20 @@
 
 We will deprecate this, the old interface, in some future release.
 """
-from __future__ import division, print_function
 import warnings
 import struct
 import itertools
 
 import numpy as np
 import numpy.linalg as npl
+from numpy.compat.py3k import asstr
 
-from .py3k import asstr
 from .volumeutils import (native_code, swapped_code, endian_codes, rec2dict)
 from .openers import ImageOpener
 from .orientations import aff2axcodes
 from .affines import apply_affine
 from .deprecated import deprecate_with_version
 
-try:
-    basestring
-except NameError:  # python 3
-    basestring = str
-
 warnings.warn("The trackvis interface has been deprecated and will be removed "
               "in v4.0; please use the 'nibabel.streamlines' interface.",
               DeprecationWarning,
@@ -326,7 +320,7 @@ def write(fileobj, streamlines, hdr_mapping=None, endianness=None,
     >>> pts1 = np.random.uniform(size=(10,3))
     >>> streamlines = ([(pts0, None, None), (pts1, None, None)])
     >>> write(file_obj, streamlines)
-    >>> _ = file_obj.seek(0) # returns 0 in python 3
+    >>> _ = file_obj.seek(0)  # returns 0
     >>> streams, hdr = read(file_obj)
     >>> len(streams)
     2
@@ -832,15 +826,13 @@ def __init__(self,
     @classmethod
     def from_file(klass, file_like, points_space=None):
         streamlines, header = read(file_like, points_space=points_space)
-        filename = (file_like if isinstance(file_like, basestring)
-                    else None)
+        filename = file_like if isinstance(file_like, str) else None
         return klass(streamlines, header, None, filename, points_space)
 
     def to_file(self, file_like):
         write(file_like, self.streamlines, self.header, self.endianness,
               points_space=self.points_space)
-        self.filename = (file_like if isinstance(file_like, basestring)
-                         else None)
+        self.filename = file_like if isinstance(file_like, str) else None
 
     def get_affine(self, atleast_v2=True):
         """ Get affine from header in object
diff --git a/nibabel/viewers.py b/nibabel/viewers.py
index 7a0f4d93d7..0cdbdcb815 100644
--- a/nibabel/viewers.py
+++ b/nibabel/viewers.py
@@ -3,7 +3,6 @@
 Includes version of OrthoSlicer3D code originally written by our own
 Paul Ivanov.
 """
-from __future__ import division, print_function
 
 import numpy as np
 import weakref
diff --git a/nibabel/volumeutils.py b/nibabel/volumeutils.py
index 95c7af3e45..2cc083ecb6 100644
--- a/nibabel/volumeutils.py
+++ b/nibabel/volumeutils.py
@@ -7,7 +7,6 @@
 #
 ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ##
 ''' Utility functions for analyze-like formats '''
-from __future__ import division, print_function
 
 import sys
 import warnings
@@ -480,7 +479,7 @@ def array_from_file(shape, in_dtype, infile, offset=0, order='F', mmap=True):
     >>> from io import BytesIO
     >>> bio = BytesIO()
     >>> arr = np.arange(6).reshape(1,2,3)
-    >>> _ = bio.write(arr.tostring('F')) # outputs int in python3
+    >>> _ = bio.write(arr.tostring('F'))  # outputs int
     >>> arr2 = array_from_file((1,2,3), arr.dtype, bio)
     >>> np.all(arr == arr2)
     True
@@ -610,7 +609,7 @@ def array_to_file(data, fileobj, out_dtype=None, offset=0,
     >>> array_to_file(data, sio, np.float)
     >>> sio.getvalue() == data.tostring('F')
     True
-    >>> _ = sio.truncate(0); _ = sio.seek(0) # outputs 0 in python 3
+    >>> _ = sio.truncate(0); _ = sio.seek(0)  # outputs 0
     >>> array_to_file(data, sio, np.int16)
     >>> sio.getvalue() == data.astype(np.int16).tostring()
     True
diff --git a/nisext/py3builder.py b/nisext/py3builder.py
index 9435f6c60b..4f82a8cfb2 100644
--- a/nisext/py3builder.py
+++ b/nisext/py3builder.py
@@ -1,6 +1,5 @@
 """ distutils utilities for porting to python 3 within 2-compatible tree """
 
-from __future__ import division, print_function, absolute_import
 
 import sys
 import re
diff --git a/nisext/testers.py b/nisext/testers.py
index a80bbd904b..e0ca4a040a 100644
--- a/nisext/testers.py
+++ b/nisext/testers.py
@@ -29,7 +29,6 @@
 
 '''
 
-from __future__ import print_function
 
 import os
 import sys
diff --git a/nisext/tests/test_testers.py b/nisext/tests/test_testers.py
index 336677b48f..08fa70cd1a 100644
--- a/nisext/tests/test_testers.py
+++ b/nisext/tests/test_testers.py
@@ -1,6 +1,5 @@
 """ Tests for testers
 """
-from __future__ import division, print_function
 
 import os
 from os.path import dirname, pathsep
diff --git a/requirements.txt b/requirements.txt
index 6299333665..365f19556b 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,9 +1,2 @@
-# Minumum requirements
-#
-# Check these against
-#   nibabel/info.py
-#   .travis.yml
-#   doc/source/installation.rst
-
-six>=1.3
-numpy>=1.8
+# Auto-generated by tools/update_requirements.py
+numpy >=1.12
diff --git a/setup.cfg b/setup.cfg
index 69bd84afe7..7ba13660eb 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -13,8 +13,6 @@ classifiers =
     License :: OSI Approved :: MIT License
     Operating System :: OS Independent
     Programming Language :: Python
-    Programming Language :: Python :: 2.7
-    Programming Language :: Python :: 3.4
     Programming Language :: Python :: 3.5
     Programming Language :: Python :: 3.6
     Programming Language :: Python :: 3.7
@@ -29,12 +27,12 @@ provides =
     nisext
 
 [options]
-python_requires = >=2.7,!=3.0.*,!=3.1.*,!=3.2.*,!=3.3.*
+python_requires = >=3.5.1
 install_requires =
-    numpy >=1.8
-    six >=1.3
-    bz2file ; python_version < "3.0"
-tests_require = nose
+    numpy >=1.12
+tests_require =
+    nose >=0.10.1
+    mock
 test_suite = nose.collector
 zip_safe = False
 packages = find:
@@ -47,6 +45,7 @@ doc =
     sphinx >=0.3
 test =
     nose >=0.10.1
+    mock
 all =
     %(dicom)s
     %(doc)s
diff --git a/tools/refresh_readme.py b/tools/refresh_readme.py
index 59076442c7..577c10bd36 100755
--- a/tools/refresh_readme.py
+++ b/tools/refresh_readme.py
@@ -3,7 +3,6 @@
 
 Should be run from nibabel root (containing setup.py)
 """
-from __future__ import print_function
 
 import os
 import runpy
diff --git a/tools/update_requirements.py b/tools/update_requirements.py
new file mode 100755
index 0000000000..551424994c
--- /dev/null
+++ b/tools/update_requirements.py
@@ -0,0 +1,29 @@
+#!/usr/bin/env python3
+import sys
+from configparser import ConfigParser
+from pathlib import Path
+
+if sys.version_info < (3, 6):
+    print("This script requires Python 3.6 to work correctly")
+    sys.exit(1)
+
+repo_root = Path(__file__).parent.parent
+setup_cfg = repo_root / "setup.cfg"
+reqs = repo_root / "requirements.txt"
+min_reqs = repo_root / "min-requirements.txt"
+
+config = ConfigParser()
+config.read(setup_cfg)
+requirements = config.get("options", "install_requires").strip().splitlines()
+
+script_name = Path(__file__).relative_to(repo_root)
+
+lines = [f"# Auto-generated by {script_name}", ""]
+
+# Write requirements
+lines[1:-1] = requirements
+reqs.write_text("\n".join(lines))
+
+# Write minimum requirements
+lines[1:-1] = [req.replace(">=", "==").replace("~=", "==") for req in requirements]
+min_reqs.write_text("\n".join(lines))