future is the missing compatibility layer between Python 2 and
Python 3. It allows you to use a single, clean Python 3.x-compatible
codebase to support both Python 2 and Python 3 with minimal overhead.
It provides ``future`` and ``past`` packages with backports and forward
ports of features from Python 3 and 2. It also comes with ``futurize`` and
``pasteurize``, customized 2to3-based scripts that helps you to convert
either Py2 or Py3 code easily to support both Python 2 and 3 in a single
clean Py3-style codebase, module by module.