Remove Python 2 dependency from docs build

Change-Id: I0b7676caa3ef836d03d9620ae55bea1fdda72d6a

doc/source/conf.py

@@ -20,8 +20,7 @@
 # All configuration values have a default; values that are commented out
 # serve to show the default.
 
-import subprocess
-# import sys
+import os
 
 import openstackdocstheme
 
@@ -76,9 +75,8 @@ release = '1.0.0'
 #   bug_tag: Tag for categorizing the bug. Must be set manually.
 # These variables are passed to the logabug code via html_context.
 giturl = u'https://git.openstack.org/cgit/openstack/i18n/tree/doc/source'
-git_cmd = ["/usr/bin/git", "rev-parse", "HEAD"]
-gitsha = subprocess.Popen(
-    git_cmd, stdout=subprocess.PIPE).communicate()[0].strip('\n')
+git_cmd = "/usr/bin/git rev-parse HEAD"
+gitsha = os.popen(git_cmd).read().strip()
 html_context = {
     "bug_project": 'openstack-i18n',
     "bug_tag": u'i18n-contributor-guide',

tox.ini

@@ -14,7 +14,6 @@ deps = -r{toxinidir}/requirements.txt
 commands = {posargs}
 
 [testenv:docs]
-basepython = python2
 commands = sphinx-build -W -b html doc/source doc/build/html
 
 [testenv:pep8]