Add tox env and job for Django 2.2

Change-Id: I3f24ac39d01490a88ab6211879bf15ad4c6c4a61

.zuul.yaml

@@ -10,6 +10,8 @@
     check:
       jobs:
         - horizon-openstack-tox-python3-django111
+        - horizon-openstack-tox-python3-django22:
+            voting: false
     gate:
       jobs:
         - horizon-openstack-tox-python3-django111

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-envlist = py27,py37,pep8
+envlist = py27,py37,py3-{dj111,dj22},pep8
 minversion = 2.3.2
 skipsdist = True
 
@@ -15,7 +15,10 @@ deps =
   -c{env:UPPER_CONSTRAINTS_FILE:https://opendev.org/openstack/requirements/raw/branch/master/upper-constraints.txt}
   -r{toxinidir}/requirements.txt
   -r{toxinidir}/test-requirements.txt
-commands = {[unit_tests]commands}
+commands =
+  dj111: pip install django>=1.11,<2
+  dj22: pip install django>=2.2,<2.3
+  {[unit_tests]commands}
 
 [unit_tests]
 commands = python manage.py test {posargs} --settings=neutron_fwaas_dashboard.test.settings
@@ -38,12 +41,6 @@ commands =
   coverage xml --omit '.tox/cover/*' -o 'cover/coverage.xml'
   coverage html --omit '.tox/cover/*' -d 'cover/htmlcov'
 
-[testenv:py3-dj111]
-basepython = python3
-commands =
-  pip install django>=1.11,<2
-  {[unit_tests]commands}
-
 [testenv:docs]
 basepython = python3
 commands = python setup.py build_sphinx