Drop python 2.7 support and testing

OpenStack is dropping the py2.7 support in ussuri cycle.

os-win is ready with python 3 and ok to drop the
python 2.7 support.

Complete discussion & schedule can be found in
- http://lists.openstack.org/pipermail/openstack-discuss/2019-October/010142.html
- https://etherpad.openstack.org/p/drop-python2-support

Ussuri Communtiy-wide goal - https://review.opendev.org/#/c/691178/

Change-Id: I9fe9bc0335624f25d5cfb22b53e5af54a9117d29

.zuul.yaml

@@ -2,8 +2,7 @@
     templates:
       - check-requirements
       - openstack-lower-constraints-jobs
-      - openstack-python-jobs
-      - openstack-python3-train-jobs
+      - openstack-python3-ussuri-jobs
       - release-notes-jobs-python3
     gate:
       queue: os-win

releasenotes/notes/drop-py-2-7-3849027908cd8717.yaml

@@ -0,0 +1,6 @@
+---
+upgrade:
+  - |
+    Python 2.7 support has been dropped. Last release of os-win
+    to support py2.7 is OpenStack Train. The minimum version of Python now
+    supported by os-win is Python 3.6.

setup.cfg

@@ -13,8 +13,6 @@ classifier =
     License :: OSI Approved :: Apache Software License
     Operating System :: Microsoft :: Windows
     Programming Language :: Python
-    Programming Language :: Python :: 2
-    Programming Language :: Python :: 2.7
     Programming Language :: Python :: 3
     Programming Language :: Python :: 3.6
     Programming Language :: Python :: 3.7

tox.ini

@@ -1,6 +1,6 @@
 [tox]
 minversion = 2.0
-envlist = py27,py37,pep8
+envlist = py37,pep8
 skipsdist = True
 
 [testenv]