Match noqa for users with explanations

This makes the regular expression a bit more complex, and potentially
slower, but it will fix the issue where users had noqa comments with
colons followed by explanations.

Closes #178

docs/source/release-notes/3.0.3.rst

+3.0.3 -- 2016-07-28 (unreleased)
+--------------------------------
+
+- Fix ``# noqa`` comments followed by a ``:`` and explanation broken by
+  3.0.0 (See also `GitLab#178`_)
+
+
+.. links
+.. _GitLab#178:
+    https://gitlab.com/pycqa/flake8/issues/178

docs/source/release-notes/index.rst

@@ -6,6 +6,7 @@ All of the release notes that have been recorded for Flake8 are organized here
 with the newest releases first.
 
 .. toctree::
+    3.0.3
     3.0.2
     3.0.1
     3.0.0

src/flake8/defaults.py

@@ -27,7 +27,7 @@ NOQA_INLINE_REGEXP = re.compile(
     # We do not care about the ``: `` that follows ``noqa``
     # We do not care about the casing of ``noqa``
     # We want a comma-separated list of errors
-    '# noqa(?:: (?P<codes>[A-Z0-9,]+))?',
+    '# noqa(?:: (?P<codes>([A-Z][0-9]+,?)+))?',
     re.IGNORECASE
 )
 

tests/unit/test_style_guide.py

@@ -130,6 +130,7 @@ def test_should_report_error(select_list, ignore_list, error_code, expected):
     ('E111', 'a = 1  # noqa, analysis:ignore', True),
     ('E111', 'a = 1  # noqa analysis:ignore', True),
     ('E111', 'a = 1  # noqa - We do not care', True),
+    ('E111', 'a = 1  # noqa: We do not care', True),
 ])
 def test_is_inline_ignored(error_code, physical_line, expected_result):
     """Verify that we detect inline usage of ``# noqa``."""