Six is a Python 2 and 3 compatibility library. It provides utility functions
for smoothing over the differences between the Python versions with the goal
of writing Python code that is compatible on both Python versions. See the
documentation for more information on what is provided.
Six supports Python 2.7 and 3.3+. It is contained in only one Python file, so
it can be easily copied into your project. (The copyright and license notice
must be retained.)