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 classifiers
- This repo has no docs, remove releasenotes and docs building
infrastructure
- Cleanup */source/conf.py to remove now obsolete content.
- Remove install_command from tox.ini, the default is fine
- Remove Babel from requirements, it's not needed for running.
- Use TOX_CONSTRAINTS_FILE, UPPER_CONSTRAINTS_FILE is obsolete
- Update to hacking 3.0, fix problems found
Change-Id: I9133baec6cb123440f34b8c4b31001cfe875919e
