sphinx docs fail on python2-default systems

Sphinx runs the default python interrupter for generating the documentation. This is annoying/a problem for systems that default to python2.7 for the python command.

A workaround for this is to make a copy of the sphinx-build script from /usr/bin and change the header to explicitly call python 3. Alternatively create an additional script for this case and change the following in the Makefile

SPHINXBUILD = sphinx-build

As per http://stackoverflow.com/questions/8015225/how-to-force-sphinx-to-use-python-3-x-interpreter

#!/usr/bin/python3
# -*- coding: utf-8 -*-
"""
Same as /usr/bin/sphinx-build but with different
interpreter
"""

import sys

if __name__ == '__main__':
    from sphinx import main, make_main
    if sys.argv[1:2] == ['-M']:
        sys.exit(make_main(sys.argv))
    else:
        sys.exit(main(sys.argv))

I could not find an obvious and nice work around for this, thus the issue instead of a PR