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: I3cd4ad5c3fe590cb1522b2be1b2059d7c70b45cc

lower-constraints.txt

@@ -18,7 +18,7 @@ django-appconf==1.0.2
 django-babel==0.6.2
 django-compressor==2.0
 django-pyscss==2.0.2
-Django==1.11
+Django==2.2
 docutils==0.11
 dogpile.cache==0.6.2
 eventlet==0.18.2
@@ -30,7 +30,7 @@ funcsigs==1.0.0
 futurist==1.2.0
 greenlet==0.4.10
 hacking==0.12.0
-horizon==14.0.0.0b3
+horizon==17.1.0
 idna==2.6
 imagesize==0.7.1
 iso8601==0.1.11
@@ -90,7 +90,7 @@ pyScss==1.3.4
 python-cinderclient==3.3.0
 python-dateutil==2.5.3
 python-glanceclient==2.8.0
-python-keystoneclient==3.8.0
+python-keystoneclient==3.22.0
 python-mimeparse==1.6.0
 python-monascaclient==1.8.0
 python-neutronclient==6.7.0

requirements.txt

@@ -3,5 +3,5 @@
 # process, which may cause wedges in the gate later.
 oslo.log>=3.36.0 # Apache-2.0
 python-monascaclient>=1.8.0 # Apache-2.0
-horizon>=14.0.0.0b3 # Apache-2.0
+horizon>=17.1.0 # Apache-2.0
 six>=1.10.0 # MIT

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-envlist = py37,py3-{dj111,dj22},pep8
+envlist = py37,pep8
 minversion = 2.6
 skipsdist = True
 
@@ -21,8 +21,6 @@ whitelist_externals =
     /bin/bash
     find
 commands =
-    dj111: pip install django>=1.11,<2
-    dj22: pip install django>=2.2,<2.3
     find . -type f -name "*.pyc" -delete
     /bin/bash run_tests.sh -N {posargs}