Add python3 django 1.11 job instead of django 2.0 job

Django 2.0 is now used in tox py35 job, so there is no need for
py35dj20 job. Instead, Django 1.11 with python3 is not covered.

- py35dj20 job is dropped from tox.ini.
- python3-django111 is added to tox.ini.
  python3 is specified to basepython to avoid a specific python version.
- Zuul job to consume python3-django111 is added.

Note that horizon-openstack-tox-py35dj20 cannot be dropped
because this job is used by horizon plugins.

Change-Id: Ic3b5e06d591a6f1d667993d19dcddfaf40882dee

.zuul.yaml

@@ -15,6 +15,14 @@
     vars:
       tox_envlist: py35dj20
 
+- job:
+    name: horizon-openstack-tox-python3-django111
+    parent: horizon-openstack-tox-base
+    vars:
+      tox_envlist: py3-dj111
+    required-projects:
+      - name: openstack/horizon
+
 - job:
     name: horizon-selenium-headless
     parent: horizon-openstack-tox-base
@@ -54,13 +62,13 @@
 - project:
     check:
       jobs:
-        - horizon-openstack-tox-py35dj20
+        - horizon-openstack-tox-python3-django111
         - horizon-selenium-headless
         - horizon-dsvm-tempest-plugin
         - openstack-tox-lower-constraints
     gate:
       jobs:
-        - horizon-openstack-tox-py35dj20
+        - horizon-openstack-tox-python3-django111
         - horizon-selenium-headless
         - horizon-dsvm-tempest-plugin
         - openstack-tox-lower-constraints

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-envlist = pep8,py27,py35,py35dj20,releasenotes,npm
+envlist = pep8,py27,py35,py3-dj111,releasenotes,npm
 minversion = 2.3.2
 skipsdist = True
 
@@ -32,12 +32,10 @@ setenv =
   {[testenv]setenv}
 commands = {[unit_tests]commands}
 
-[testenv:py35dj20]
-basepython = python3.5
-deps =
-  -r{toxinidir}/test-requirements.txt
+[testenv:py3-dj111]
+basepython = python3
 commands =
-  pip install django>=2.0,<2.1
+  pip install django>=1.11,<2
   {[unit_tests]commands}
 
 [unit_tests]