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: Iffde0ffc4a8f640e58ce3beb5706186ca038eede
Story: #2005924
Task: #34200

1 files changed, 1 insertions, 1 deletions

diff --git a/tox.ini b/tox.ini
index e4d3db4..8b288d1 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,6 +1,6 @@
 [tox]
 distribute = False
-envlist = py36,py27,pep8
+envlist = py27,py37,pep8
 minversion = 2.0
 skipsdist = True