Update docs building:
* Switch to sphinx-build
* Update requirements for Sphinx and openstackdocstheme for
python 3, create doc/requiremetns
* Remove unneeded doc and translation sections from setup.cfg
* Remove install_command, it's unneeded, the default is fine.
* Move constraints to deps, use TOX_CONSTRAINTS instead of obsolete
UPPER_CONSTRAINTS
* Remove now unneeded placeholder file
Change-Id: I649e6fa86c17262698cc8a01d042a87b020239d9
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 anymor
Change-Id: I3f780c21e6867a394e1797e67099f1668388f6a7