This repo is now testing only with Python 3, so let's make
a few cleanups:
- Remove python 2.7 stanza from setup.py
- Remove obsolete sections from setup.cfg
- Update requirements, no need for python_version anymore
- Cleanup */source/conf.py to remove now obsolete content.
- Use newer openstackdocstheme version
- Remove install_command from tox.ini, the default is fine
- Enable warnings for doc builds, fix doc build problems
Change-Id: Id1ecc85694dddd177dde628a031b7cb637932fbc
1d3fa5934d