Minor addition to README to try to explain PR, minor change to setup.py to reflect deprecation of Python 2.7 support, and attempt to remove as many of the Python 2.7 import statements as possible.

Author: krinsman

README.md

@@ -185,6 +185,12 @@ If you'd like to write a new format, open a ticket, or speak up on [gitter][]!
 We have some work yet to do to support your next big thing in notebook
 publishing, and we'd love to here from you.
 
+#### Config file
+
+Newer versions of NBViewer will be configurable using a config file, `nbviewer_config.py`. In the directory where you run the command `python -m nbviewer` to start NBViewer, also add a file `nbviewer_config.py` which uses [the standard configuration syntax for Jupyter projects](https://traitlets.readthedocs.io/en/stable/config.html). 
+
+For example, to configure the value of a configurable `foo`, add the line `c.NBViewer.foo = 'bar'` to the `nbviewer_config.py` file located where you run `python -m nbviewer`. Again, currently very few features of NBViewer are configurable this way, but we hope to steadily increase the number of configurable characteristics of NBViewer in future releases.
+
 ## Securing the Notebook Viewer
 
 You can run the viewer as a [JupyterHub 0.7+ service](https://jupyterhub.readthedocs.io/en/latest/reference/services.html). Running the viewer as a service prevents users who have not authenticated with the Hub from acccessing the nbviewer instance. This setup can be useful for protecting access to local notebooks rendered with the `--localfiles` option.

nbviewer/app.py

@@ -12,17 +12,8 @@
 import logging
 import markdown
 
-
-try:
-    # py3
-    from urllib.parse import urlparse
-    # https://docs.python.org/3/library/cgi.html#cgi.escape
-    # Deprecated since version 3.2: This function is unsafe because quote is
-    # false by default, and therefore deprecated. Use html.escape() instead.
-    from html import escape
-except ImportError:
-    from cgi import escape
-    from urlparse import urlparse
+from urllib.parse import urlparse
+from html import escape
 
 from concurrent.futures import ThreadPoolExecutor, ProcessPoolExecutor
 

nbviewer/cache.py

@@ -6,10 +6,7 @@
 #-----------------------------------------------------------------------------
 
 import zlib
-try:
-    from time import monotonic
-except ImportError:
-    from time import time as monotonic
+from time import monotonic
 
 from concurrent.futures import ThreadPoolExecutor
 from tornado.concurrent import Future

nbviewer/providers/base.py

@@ -15,14 +15,8 @@
 from contextlib import contextmanager
 from datetime import datetime
 
-try:
-    # py3
-    from http.client import responses
-    from urllib.parse import urlparse, urlunparse, quote, urlencode
-except ImportError:
-    from httplib import responses
-    from urlparse import urlparse, urlunparse
-    from urllib import quote, urlencode
+from http.client import responses
+from urllib.parse import urlparse, urlunparse, quote, urlencode
 
 from tornado import (
     gen,

nbviewer/providers/github/client.py

@@ -8,10 +8,7 @@
 import json
 import os
 
-try: # py3
-    from urllib.parse import urlparse
-except ImportError:
-    from urlparse import urlparse
+from urllib.parse import urlparse
 
 from tornado.concurrent import Future
 from tornado.httpclient import AsyncHTTPClient, HTTPError

nbviewer/providers/url/handlers.py

@@ -5,13 +5,8 @@
 #  the file COPYING, distributed as part of this software.
 #-----------------------------------------------------------------------------
 
-try:
-    # py3
-    from urllib.parse import urlparse
-    from urllib import robotparser
-except ImportError:
-    from urlparse import urlparse
-    import robotparser
+from urllib.parse import urlparse
+from urllib import robotparser
 
 from tornado import (
     gen,

nbviewer/utils.py

@@ -5,36 +5,22 @@
 #  the file COPYING, distributed as part of this software.
 #-----------------------------------------------------------------------------
 
-# https://docs.python.org/3.1/library/base64.html#base64.decodestring
-try:
-    from base64 import encodebytes
-    from base64 import decodebytes
-except ImportError:
-    from base64 import encodestring as encodebytes
-    from base64 import decodestring as decodebytes
+from base64 import encodebytes
+from base64 import decodebytes
 
 import cgi
 from contextlib import contextmanager
 import re
 from subprocess import check_output
 import time
 
-try:
-    from urllib.parse import (
-        parse_qs,
-        quote as stdlib_quote,
-        urlencode,
-        urlparse,
-        urlunparse,
-    )
-except ImportError:
-    from urllib import urlencode
-    from urllib2 import quote as stdlib_quote
-    from urlparse import (
-        parse_qs,
-        urlparse,
-        urlunparse,
-    )
+from urllib.parse import (
+    parse_qs,
+    quote as stdlib_quote,
+    urlencode,
+    urlparse,
+    urlunparse,
+)
 
 from tornado.log import app_log
 

setup.py

@@ -78,8 +78,6 @@ def walk_subpkg(name):
     license = "BSD",
     classifiers = [
         'License :: OSI Approved :: BSD License',
-        'Programming Language :: Python :: 2',
-        'Programming Language :: Python :: 2.7',
         'Programming Language :: Python :: 3',
         'Programming Language :: Python :: 3.3',
     ],