This repo is now testing only with Python 3, so let's make
a few cleanups:
- Remove python 2.7 stanza from setup.py
- 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 classifiers
- Update requirements, no need for python_version anymore
- Switch to using sphinx-build with apidoc extension
- Use newer openstackdocstheme version
- Remove Babel requirement, this is not needed.
Change-Id: I4176d8002d45449171aa5f7a7caef196ab7900d0
1a8c1bb370