Add Python 3.6 and Python 3.7 jobs

According to 'Tested Runtimes for Train' [1] we need to support
Python 2.7, Python 3.7 and Python 3.6 runtimes.

[1] https://governance.openstack.org/tc/reference/runtimes/train.html

Change-Id: I75f56a0fe753bcc1250c4aaf8f191f4bad7d0028

.zuul.yaml

@@ -4,6 +4,8 @@
       - openstack-cover-jobs-horizon
       - openstack-lower-constraints-jobs-horizon
       - openstack-python-jobs-horizon
+      - openstack-python36-jobs-horizon
+      - openstack-python37-jobs-horizon
       - publish-openstack-docs-pti
       - release-notes-jobs-python3
     check:

setup.cfg

@@ -17,6 +17,7 @@ classifier =
     Programming Language :: Python :: 2.7
     Programming Language :: Python :: 3
     Programming Language :: Python :: 3.6
+    Programming Language :: Python :: 3.7
 
 [files]
 packages =

tox.ini

@@ -1,6 +1,6 @@
 [tox]
 minversion = 1.6
-envlist = py27,pep8,py27dj19,py27dj110,py3-dj111
+envlist = py37,py36,py27,pep8,py27dj19,py27dj110,py3-dj111
 skipsdist = True
 
 [testenv]
@@ -18,6 +18,9 @@ setenv = DJANGO_SETTINGS_MODULE=manila_ui.tests.settings
 [testenv:py36]
 setenv = DJANGO_SETTINGS_MODULE=manila_ui.tests.settings
 
+[testenv:py37]
+setenv = DJANGO_SETTINGS_MODULE=manila_ui.tests.settings
+
 [testenv:py3-dev]
 setenv = DJANGO_SETTINGS_MODULE=manila_ui.tests.settings
 commands =