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: I182dbda3e602e15bac229518e3e0704f7ee6a4c9

.zuul.yaml

@@ -83,7 +83,6 @@
 - project:
     templates:
       - openstack-python-jobs
-      - openstack-python35-jobs
       - openstack-python36-jobs
       - openstack-python37-jobs
       - publish-openstack-docs-pti
@@ -97,9 +96,6 @@
               - ^.zuul.yaml$
             required-projects:
               - openstack/mistral-lib
-        - openstack-tox-py35:
-            required-projects:
-              - openstack/mistral-lib
         - openstack-tox-py36:
             required-projects:
               - openstack/mistral-lib

setup.cfg

@@ -10,7 +10,6 @@ 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

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-envlist = py37,py36,py35,py27,pep8
+envlist = py37,py36,py27,pep8
 minversion = 2.0
 skipsdist = True