Add Python 3 Train unit tests

This is a mechanically generated patch to ensure unit testing is in place
for all of the Tested Runtimes for Train.

See the Train python3-updates goal document for details:
https://governance.openstack.org/tc/goals/train/python3-updates.html

Change-Id: Ie47812bec5284d447a2f9c339a5b29d49d83ab53
Story: #2005924
Task: #34234

1 files changed, 1 insertions, 1 deletions

diff --git a/tox.ini b/tox.ini
index 9ae5a49..ce09ed3 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,6 +1,6 @@
 [tox]
 minversion = 2.0
-envlist = py27,py36,pep8
+envlist = py27,py37,pep8
 
 [testenv]
 whitelist_externals =