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:
* Wheel is not needed for python 3 only repo
* Some other sections are obsolete
- Update classifiers
- Update requirements, no need for python_version anymore
Change-Id: I57dc2210d369cb89ad2de7d2c304a8f225fd6adf
See https://review.openstack.org/283511 for history.
Change-Id: I7733e8786d6b525a7c9a8d4f12add329cd030d9d
Partially-Implements: blueprint designate-tempest-plugin