Drop python 2.7 support and testing

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

watcher-dashboard 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: Ibc21e289b146e7c4ce4a5c20198c1d26fd97b604

.zuul.yaml

@@ -3,7 +3,6 @@
       - check-requirements
       - horizon-non-primary-django-jobs
       - openstack-lower-constraints-jobs
-      - openstack-python-jobs-horizon
       - openstack-python3-ussuri-jobs-horizon
       - publish-openstack-docs-pti
       - release-notes-jobs-python3

releasenotes/notes/drop-py-2-7-198cca7f72d16655.yaml

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

setup.cfg

@@ -17,8 +17,6 @@ classifier =
     Operating System :: OS Independent
     Operating System :: POSIX :: Linux
     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 = py37,py36,py27,py3-{dj111,dj22},pep8
+envlist = py37,py36,py3-{dj111,dj22},pep8
 skipsdist = True
 
 [testenv]
@@ -35,10 +35,6 @@ commands = flake8
 basepython = python3
 commands = {posargs}
 
-[testenv:py27integration]
-basepython = python2.7
-commands = /bin/bash run_tests.sh -N --integration --selenium-headless {posargs}
-
 [testenv:releasenotes]
 basepython = python3
 commands = sphinx-build -a -E -W -d releasenotes/build/doctrees -b html releasenotes/source releasenotes/build/html