Rely on Python 3.4 backport of configparser

Python 2.7's ConfigParser module does not allow for the behaviour we
have documented for config files in Flake8 3.0. To compensate for that,
we add a dependency on the configparser backport on PyPI for Python 2.7

docs/source/user/configuration.rst

@@ -155,6 +155,14 @@ This would allow us to add comments for why we're excluding items, e.g.,
         dist
     max-complexity = 10
 
+.. note::
+
+    If you're using Python 2, you will notice that we download the
+    :mod:`configparser` backport from PyPI. That backport enables us to
+    support this behaviour on all supported versions of Python.
+
+    Please do **not** open issues about this dependency.
+
 .. note::
 
     You can also specify ``--max-complexity`` as ``max_complexity = 10``.

flake8/options/config.py

@@ -1,13 +1,9 @@
 """Config handling logic for Flake8."""
+import configparser
 import logging
 import os.path
 import sys
 
-if sys.version_info < (3, 0):
-    import ConfigParser as configparser
-else:
-    import configparser
-
 LOG = logging.getLogger(__name__)
 
 __all__ = ('ConfigFileFinder', 'MergedConfigParser')

setup.cfg

@@ -7,6 +7,7 @@ universal=1
 [metadata]
 requires-dist =
     enum34; python_version<"3.4"
+    configparser; python_version<"3.2"
 
 [pytest]
 norecursedirs = .git .* *.egg* old docs dist build

setup.py

@@ -31,7 +31,7 @@ if mock is None:
 requires = [
     "pyflakes >= 0.8.1, < 1.1",
     "pep8 >= 1.5.7, != 1.6.0, != 1.6.1, != 1.6.2",
-    # "mccabe >= 0.2.1, < 0.4",
+    "mccabe >= 0.2.1, < 0.4",
 ]
 
 if sys.version_info < (3, 4):

tests/unit/test_config_file_finder.py

@@ -1,9 +1,5 @@
 """Tests for the ConfigFileFinder."""
-try:
-    import ConfigParser as configparser
-except ImportError:
-    import configparser
-
+import configparser
 import os
 import sys
 

tox.ini

@@ -6,6 +6,7 @@ envlist = py27,py33,py34,py35,flake8
 deps =
     mock
     pytest
+    py27: configparser
 commands =
     py.test {posargs}