Drop python 2.7 support and testing

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

zun-ui 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: I9134e73c6698e225044282977f40298822280b1c

.zuul.yaml

@@ -4,7 +4,6 @@
       - horizon-non-primary-django-jobs
       - horizon-nodejs10-jobs
       - openstack-lower-constraints-jobs-horizon
-      - openstack-python-jobs-horizon
       - openstack-python3-ussuri-jobs-horizon
       - publish-openstack-docs-pti
       - release-notes-jobs-python3

releasenotes/notes/drop-py-2-7-e15513672c769acb.yaml

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

setup.cfg

@@ -13,8 +13,6 @@ classifier =
     License :: OSI Approved :: Apache Software License
     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

@@ -1,5 +1,5 @@
 [tox]
-envlist = pep8,py37,py27-local,py36-local,py3-{dj111,dj22},eslint,karma-local,docs-local,releasenotes,lower-constraints-local
+envlist = pep8,py37,py36-local,py3-{dj111,dj22},eslint,karma-local,docs-local,releasenotes,lower-constraints-local
 minversion = 2.3.2
 skipsdist = True
 
@@ -50,12 +50,6 @@ commands = python setup.py test --coverage --testr-args='{posargs}'
 # NOTE(shu-mutow): On CI infra, horizon will be installed
 # according to job setting. but on local, we need to install
 # horizon from master branch.
-[testenv:py27-local]
-basepython = python2.7
-commands =
-  {[testenv:hz-local]commands}
-  {[testenv]commands}
-
 [testenv:py36-local]
 basepython = python3.6
 commands =