Cleanup py27 support

This repo is now testing only with Python 3, so let's make
a few cleanups:
- Remove setup.* files, those are not needed for this repo.
- Cleanup */source/conf.py to remove now obsolete content.
- Remove install_command from tox.ini, the default is fine,
  move constraints into deps
- Enable warnings for docs build

Change-Id: I07da37d6f15aefc7b2fa558a6ead7028d6c9c556

releasenotes/source/conf.py

@@ -62,11 +62,6 @@ role_name = 'rabbitmq_server'
 target_name = 'openstack-ansible-' + role_name
 title = 'OpenStack-Ansible Release Notes: ' + role_name + 'role'
 
-# The link to the browsable source code (for the left hand menu)
-oslosphinx_cgit_link = (
-    'https://opendev.org/openstack/{}'.format(target_name)
-)
-
 # Release notes do not need a version number in the title, they
 # cover multiple releases.
 # The full version, including alpha/beta/rc tags.
@@ -158,10 +153,6 @@ html_static_path = ['_static']
 # directly to the root of the documentation.
 # html_extra_path = []
 
-# If not '', a 'Last updated on:' timestamp is inserted at every page bottom,
-# using the given strftime format.
-html_last_updated_fmt = '%Y-%m-%d %H:%M'
-
 # If true, SmartyPants will be used to convert quotes and dashes to
 # typographically correct entities.
 # html_use_smartypants = True