Cleanup py27 support

This repo is now testing only with Python 3, so let's make
a few cleanups:
- Update requirements, no need for python_version anymore
- Cleanup doc/source/conf.py to remove now obsolete content.
- Use newer openstackdocstheme version
- Remove install_command from tox.ini, the default is fine

Change-Id: I7582abcbf237320b0707732270388f113d93349d

doc/source/conf.py

@@ -133,11 +133,6 @@ html_title = 'OpenStack SIGs Governance'
 # so a file named "default.css" will overwrite the builtin "default.css".
 html_static_path = ['_static']
 
-# If not '', a 'Last updated on:' timestamp is inserted at every page bottom,
-# using the given strftime format.
-git_cmd = "git log --pretty=format:'%ad, commit %h' --date=local -n1"
-html_last_updated_fmt = os.popen(git_cmd).read()
-
 # If true, SmartyPants will be used to convert quotes and dashes to
 # typographically correct entities.
 #html_use_smartypants = True

test-requirements.txt

@@ -3,7 +3,6 @@
 # process, which may cause wedges in the gate later.
 # needed for doc build
 docutils>=0.11,!=0.13.1  # OSI-Approved Open Source, Public Domain
-sphinx!=1.6.6,!=1.6.7,>=1.6.2,<2.0.0;python_version=='2.7' # BSD
-sphinx!=1.6.6,!=1.6.7,!=2.1.0,>=1.6.2;python_version>='3.4' # BSD
-openstackdocstheme>=1.25.1  # Apache-2.0
+sphinx!=1.6.6,!=1.6.7,!=2.1.0,>=1.6.2 # BSD
+openstackdocstheme>=1.31.2  # Apache-2.0
 yamllint

tox.ini

@@ -5,7 +5,6 @@ skipsdist = True
 
 [testenv]
 usedevelop = True
-install_command = pip install -U {opts} {packages}
 setenv = VIRTUAL_ENV={envdir}
 deps = -r{toxinidir}/test-requirements.txt
 basepython = python3