RF: Use builtin FileNotFoundError

Author: effigies

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
 
 

nibabel/tests/test_loadsave.py

@@ -21,7 +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')