Drop Django 1.11 support

Django 1.11 ends its extended support in April 2020 (which is before
Ussuri release), so horizon drops Django 1.11 support in Ussuri.

tox envs for non-primary Django versions are no longer needed in tox.ini
as testing environments for non-primary Django versions are setup in
the zuul jobs now.

horizon>=17.1.0 is required to use Django 2.2. requirements.txt and
lower-constraints.txt are updated accordingly. for more info. please
refer [1].
Depends-On: https://review.opendev.org/#/c/700733/
[1] https://etherpad.openstack.org/p/Enable_Django22_support_in_Horizon_Plugin

Change-Id: I29cd34d17a00eb1b576f46d6010203603b5c8165

lower-constraints.txt

@@ -17,7 +17,7 @@ django-appconf==1.0.2
 django-babel==0.6.2
 django-compressor==2.2
 django-pyscss==2.0.2
-Django==1.11.11
+Django==2.2
 docutils==0.14
 dogpile.cache==0.6.5
 dulwich==0.19.0
@@ -27,6 +27,7 @@ fixtures==3.0.0
 flake8==2.5.5
 futurist==1.6.0
 hacking==0.12.0
+horizon==17.1.0
 idna==2.6
 imagesize==1.0.0
 iso8601==0.1.12

requirements.txt

@@ -4,3 +4,4 @@
 
 pbr!=2.1.0,>=2.0.0 # Apache-2.0
 python-ironicclient!=2.5.2,!=2.7.1,>=2.3.0 # Apache-2.0
+horizon>=17.1.0  # Apache-2.0

test-requirements.txt

@@ -11,9 +11,6 @@ testrepository>=0.0.18 # Apache-2.0/BSD
 testscenarios>=0.4 # Apache-2.0/BSD
 testtools>=2.2.0 # MIT
 
-# Include horizon as test requirement
-http://tarballs.openstack.org/horizon/horizon-master.tar.gz#egg=horizon
-
 # integration tests requirements
 selenium>=2.50.1 # Apache-2.0
 xvfbwrapper>=0.1.3 #license: MIT

tox.ini

@@ -1,7 +1,7 @@
 [tox]
 minversion = 1.8
 skipsdist = True
-envlist = py3,py3-{dj111,dj22},pep8
+envlist = py3,pep8
 
 [testenv]
 usedevelop = True
@@ -17,8 +17,6 @@ setenv = VIRTUAL_ENV={envdir}
 deps = -r{toxinidir}/requirements.txt
        -r{toxinidir}/test-requirements.txt
 commands =
-   dj111: pip install django>=1.11,<2
-   dj22: pip install django>=2.2,<2.3
    {toxinidir}/manage.py test ironic_ui --settings=ironic_ui.test.settings --exclude-tag integration
 
 [testenv:integration]