This repo is now testing only with Python 3, so let's make
a few cleanups:
- Add requires on python >= 3.6 to setup.cfg so that pypi and pip
know about the requirement
- Remove obsolete sections from setup.cfg
- Update requirements, no need for python_version anymore
- Use newer openstackdocstheme and Sphinx versions
- Remove install_command from tox.ini, the default is fine
- Remove babel.cfg, it's not needed
- move basepython into testenv
Change-Id: I4c0e3b9b12c6b46c3b6b6a2f8f96e6996421dd8d
Andreas Jaeger