replace six dependency by future - #2

python-future is a higher-level compatibility layer than six that includes more backported functionality from Python 3, more forward-ported functionality from Python 2, and supports cleaner code, but requires more modern Python versions to run.

python-future and six share the same goal of making it possible to write a single-source codebase that works on both Python 2 and Python 3. python-future has the further goal of allowing standard Py3 code to run with almost no modification on both Py3 and Py2. future provides a more complete set of support for Python 3’s features, including backports of Python 3 builtins such as the bytes object (which is very different to Python 2’s str object) and several standard library modules.

future is the way to go.