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: Id9ed3cec95f0e0203ef00dd5ff10d124913e39f2
Story: #2005924
Task: #34209

1 files changed, 1 insertions, 1 deletions

diff --git a/tox.ini b/tox.ini
index 0861ad2..117ae5f 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,5 +1,5 @@
 [tox]
-envlist = pypy,py36,py27,pep8
+envlist = pypy,py27,py37,pep8
 minversion = 2.0
 skipsdist = True