Replace six with the current version which passes checklicenses.py.

third_party/six/setup.py

+# Copyright (c) 2010-2015 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.
+
 from __future__ import with_statement
 
 try:
     from setuptools import setup
 except ImportError:
     from distutils.core import setup
 
 import six
 
 six_classifiers = [
@@ skipping 12 matching lines @@
       version=six.__version__,
       author="Benjamin Peterson",
       author_email="benjamin@python.org",
       url="http://pypi.python.org/pypi/six/",
       py_modules=["six"],
       description="Python 2 and 3 compatibility utilities",
       long_description=six_long_description,
       license="MIT",
       classifiers=six_classifiers
       )