[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/releasenotes/notes/drop-py-2-7-730baf411876d5d8.yaml b/releasenotes/notes/drop-py-2-7-730baf411876d5d8.yaml
new file mode 100644
index 0000000..a0ac244
--- /dev/null
+++ b/releasenotes/notes/drop-py-2-7-730baf411876d5d8.yaml
@@ -0,0 +1,6 @@
+---
+upgrade:
+  - |
+    Python 2.7 support has been dropped. Last release of Tempest
+    to support python 2.7 is Temepst 23.0.0. The minimum version of Python now
+    supported by Tempest is Python 3.6.