Cleanup py27 support

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
- Use newer openstackdocstheme and Sphinx versions
- Cleanup */source/conf.py to remove now obsolete content.
- Remove install_command from tox.ini, the default is fine
- Remove hacking requirements from lower-constraints, they
  are not needed for install

Change-Id: I150a5ee2cd08abf5ce9cf9daf2835007dea0dffd
diff --git a/doc/requirements.txt b/doc/requirements.txt
index ae644f5..d155165 100644
--- a/doc/requirements.txt
+++ b/doc/requirements.txt
@@ -1,8 +1,8 @@
 # The order of packages is significant, because pip processes them in the order
 # of appearance. Changing the order has an impact on the overall integration
 # process, which may cause wedges in the gate later.
-sphinx!=1.6.6,!=1.6.7,!=2.1.0,>=1.6.2 # BSD
-openstackdocstheme>=1.20.0 # Apache-2.0
+sphinx>=2.0.0,!=2.1.0 # BSD
+openstackdocstheme>=2.0.0 # Apache-2.0
 reno>=2.5.0 # Apache-2.0
 sphinxcontrib-apidoc>=0.2.0  # BSD
 sphinxcontrib-svg2pdfconverter>=0.1.0 # BSD
diff --git a/doc/source/conf.py b/doc/source/conf.py
index 4fa65e6..12c20ec 100755
--- a/doc/source/conf.py
+++ b/doc/source/conf.py
@@ -89,9 +89,6 @@
 bug_project = 'patrole'
 bug_tag = ''
 
-# Must set this variable to include year, month, day, hours, and minutes.
-html_last_updated_fmt = '%Y-%m-%d %H:%M'
-
 # Output file base name for HTML help builder.
 htmlhelp_basename = 'patroledoc'
 
@@ -109,4 +106,4 @@
 ]
 
 # Disable usage of xindy https://bugzilla.redhat.com/show_bug.cgi?id=1643664
-latex_use_xindy = False
\ No newline at end of file
+latex_use_xindy = False