[ussuri][goal] Drop python 2.7 support and testing

OpenStack is dropping the py2.7 support in ussuri cycle.

Tempest is ready with python 3 and ok to drop the
python 2.7 support. Last Tempest version officially supported
for py2.7 is 23.0.0.

Now onwards, Tempest will test all stable branch with py3 jobs.
tempest-full and other py2 version of jobs definition are kept
for stable branch gate.

Complete discussion & schedule can be found in
- http://lists.openstack.org/pipermail/openstack-discuss/2019-October/010142.html
- https://etherpad.openstack.org/p/drop-python2-support

Ussuri Communtiy-wide goal:
https://governance.openstack.org/tc/goals/selected/ussuri/drop-py27.html

Change-Id: I75868d5c9b6630fe78958ff89e58a0aced09a6b3
diff --git a/doc/requirements.txt b/doc/requirements.txt
index 2194dc4..9f38ada 100644
--- a/doc/requirements.txt
+++ b/doc/requirements.txt
@@ -3,6 +3,5 @@
 # process, which may cause wedges in the gate later.
 openstackdocstheme>=1.20.0 # Apache-2.0
 reno>=2.5.0 # Apache-2.0
-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
+sphinx!=1.6.6,!=1.6.7,!=2.1.0,>=1.6.2 # BSD
 sphinxcontrib-svg2pdfconverter>=0.1.0 # BSD
diff --git a/doc/source/supported_version.rst b/doc/source/supported_version.rst
index a97ec5b..4f65fd4 100644
--- a/doc/source/supported_version.rst
+++ b/doc/source/supported_version.rst
@@ -1,7 +1,7 @@
 Supported OpenStack Releases and Python Versions
 ================================================
 
-This Document list the officially supported OpenStack releases
+This document lists the officially supported OpenStack releases
 and python versions by Tempest.
 
 Compatible OpenStack Releases
@@ -24,13 +24,13 @@
 * https://releases.openstack.org/stein/index.html#stein-tempest
 
 How to use Tempest tag on Extended Maintenance stable branch:
-* https://review.opendev.org/#/c/681950/
+
+* https://review.opendev.org/#/c/705098/
 
 Supported Python Versions
 -------------------------
 
 Tempest master supports the below python versions:
 
-* Python 2.7
 * Python 3.6
 * Python 3.7