Dropping the py35 testing

All the integration testing has been moved to
Bionic now[1] and py3.5 is not tested runtime for
Train or stable/stein[2].

As per below ML thread, we are good to drop the py35
testing now:
http://lists.openstack.org/pipermail/openstack-discuss/2019-April/005097.html

[1] http://lists.openstack.org/pipermail/openstack-discuss/2019-April/004647.html
[2]
https://governance.openstack.org/tc/reference/runtimes/stein.html
https://governance.openstack.org/tc/reference/runtimes/train.html

Change-Id: Ib68a1cb57957e5705dcdf1ee0f46cf9359a6bf47

.zuul.yaml

@@ -2,5 +2,4 @@
     templates:
       - openstack-python-jobs
       - check-requirements
-      - openstack-python35-jobs
       - openstack-python36-jobs

setup.cfg

@@ -8,7 +8,7 @@ classifiers =
     Programming Language :: Python :: 2
     Programming Language :: Python :: 2.7
     Programming Language :: Python :: 3
-    Programming Language :: Python :: 3.5
+    Programming Language :: Python :: 3.6
     Environment :: OpenStack
     Intended Audience :: Information Technology
     Intended Audience :: System Administrators

tox.ini

@@ -1,6 +1,6 @@
 [tox]
 minversion = 2.0
-envlist = pep8,py27,py35
+envlist = pep8,py27,py36
 skipsdist = True
 
 [testenv]
@@ -49,8 +49,8 @@ exclude=.venv,.git,.tox,dist,doc,*lib/python*,*egg,build,.ropeproject,tools,hori
 basepython = python3
 commands = sphinx-build -a -E -W -d releasenotes/build/doctrees -b html releasenotes/source releasenotes/build/html
 
-[testenv:py35dj20]
-basepython = python3.5
+[testenv:py36dj20]
+basepython = python3.6
 commands =
   pip install django>=2.0,<2.1
-  {[testenv]commands}
+  {[testenv]commands}