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
- Switch to using sphinx-build
- Use openstackdocstheme instead of python2 only oslosphinx
- Remove install_command from tox.ini, the default is fine
- Fix two hacking problems, those were masked by ignore
to an empty string.
Change-Id: I8f67f8a7998a16805cbda52854a6b0f0ade05dc8