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: I810c1731659213457558eec31873ab4807a8d1c3

.zuul.yaml

@@ -52,7 +52,6 @@
     templates:
       - openstack-cover-jobs
       - openstack-python-jobs
-      - openstack-python35-jobs
       - openstack-python36-jobs
       - openstack-python37-jobs
       - check-requirements

setup.cfg

@@ -16,7 +16,7 @@ classifier =
     Programming Language :: Python :: 2
     Programming Language :: Python :: 2.7
     Programming Language :: Python :: 3
-    Programming Language :: Python :: 3.5
+    Programming Language :: Python :: 3.6
 
 [global]
 setup-hooks =

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-envlist = py{27,35},pep8,cover
+envlist = py{27,36},pep8,cover
 minversion = 2.7
 skipsdist = True
 
@@ -28,9 +28,9 @@ commands =
   {[testenv]commands}
   ostestr {posargs}
 
-[testenv:py35]
-description = Runs unit test using Python3.5
-basepython = python3.5
+[testenv:py36]
+description = Runs unit test using Python3.6
+basepython = python3.6
 commands =
   {[testenv]commands}
   ostestr {posargs}