Allow both Django 2.2 and 3.2 for smooth transition

I believe we need the following steps and it is what I did in past
when we bump the Django minimum version.

1. (already done) update global-requirements.txt to allow horizon to
   update requirements.txt to include Django 3.2.
2. specify the required Django version which includes both 2.2 and 3.2
   (at this point upper-constraints uses 2.2)
3. update upper-constraints.txt in the requirements repo to use Django 3.2
4. bump the min version of Django in horizon

(optionally) update non-primary-django tests to include non-primary versions of
Django. It seems you drops 2.2 support together when we support 3.2, so perhaps
this step is not the case though.

https://review.opendev.org/c/openstack/horizon/+/811412 directly updated
the min version to Django 3.2 which is incompatible with the global
upper-constraints.txt.
To avoid this, https://review.opendev.org/c/openstack/horizon/+/815206 made
almost all tests non-voting. I am not a fan of such approach and believe
there is a way to make the transition of Django version more smoothly.

---

This commit reverts the zuul configuration changes in
https://review.opendev.org/c/openstack/horizon/+/815206 and
https://review.opendev.org/c/openstack/horizon/+/811412.

horizon-tox-python3-django32 is voting now as we are making it
the default version.

Change-Id: I60bb672ef1b197e657a8b3bd86d07464bcb1759f

.zuul.d/django-jobs.yaml

@@ -38,13 +38,9 @@
         # We specify a job in openstack-python3-yoga-jobs(-horizon)
         # to keep this project template as it is used in horizon plugins.
         # NOTE: We keep it as a template even though it is not used now.
-        - openstack-tox-py38:
+        - openstack-tox-py38
-            voting: false
+        - horizon-tox-python3-django32
-        - horizon-tox-python3-django32:
-            voting: false
     gate:
       jobs:
-        - openstack-tox-py38:
+        - openstack-tox-py38
-            voting: false
+        - horizon-tox-python3-django32
-        # Skip these until the django3.x jobs become voting.
-        # - horizon-tox-python3-django32

.zuul.d/project.yaml

@@ -2,29 +2,27 @@
     templates:
       - check-requirements
       - horizon-cross-jobs
-      #- horizon-nodejs14-jobs
+      - horizon-nodejs14-jobs
       - horizon-non-primary-django-jobs
       - openstack-lower-constraints-jobs
-      #- openstack-python3-yoga-jobs
+      - openstack-python3-yoga-jobs
       - periodic-stable-jobs
-      #- publish-openstack-docs-pti
+      - publish-openstack-docs-pti
       - release-notes-jobs-python3
     check:
       jobs:
-        - horizon-selenium-headless:
+        - horizon-selenium-headless
-            voting: false
+        - horizon-integration-tests
-        #- horizon-integration-tests
+        - horizon-dsvm-tempest-plugin
-        #- horizon-dsvm-tempest-plugin
+        - horizon-tox-bandit-baseline
-        #- horizon-tox-bandit-baseline
+        - horizon-tempest-plugin-ipv6
-        #- horizon-tempest-plugin-ipv6
     gate:
       queue: horizon
       jobs:
-        #- horizon-dsvm-tempest-plugin
+        - horizon-dsvm-tempest-plugin
-        - horizon-selenium-headless:
+        - horizon-selenium-headless
-            voting: false
+        - horizon-integration-tests
-        #- horizon-integration-tests
+        - horizon-tempest-plugin-ipv6
-        #- horizon-tempest-plugin-ipv6
     experimental:
       jobs:
         - horizon-integration-tests-xstatic-master

lower-constraints.txt

@@ -15,7 +15,7 @@ cryptography==3.0
 debtcollector==1.2.0
 decorator==4.4.2
 deprecation==1.0
-Django==3.2
+Django==2.2
 django-appconf==1.0.5
 django-compressor==2.4.1
 django-debreach==1.4.2

requirements.txt

@@ -12,7 +12,7 @@ pbr>=5.5.0 # Apache-2.0
 # Horizon Core Requirements
 Babel>=2.6.0 # BSD
 debtcollector>=1.2.0 # Apache-2.0
-Django>=3.2,<3.3 # BSD
+Django>=2.2,<3.3 # BSD
 django-compressor>=2.4.1 # MIT
 django-debreach>=1.4.2 # BSD License (2 clause)
 django-pyscss>=2.0.2 # BSD License (2 clause)