[ussuri][goal] Drop python 2.7 support and testing

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

neutron-vpnass-dashboard is ready with python 3 and ok to drop the
python 2.7 support.

Also this patch update minimum tox version in tox.ini file.
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://governance.openstack.org/tc/goals/selected/ussuri/drop-py27.html

Depends-On: https://review.opendev.org/#/c/693631/

Change-Id: Iabd2e1dfb73ec03bf3ed7f8a2a6c6493f036242f

.zuul.yaml

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

doc/requirements.txt

@@ -2,7 +2,6 @@
 # of appearance. Changing the order has an impact on the overall integration
 # process, which may cause wedges in the gate later.
 
-sphinx!=1.6.6,!=1.6.7,>=1.6.2,<2.0.0;python_version=='2.7'  # BSD
 sphinx!=1.6.6,!=1.6.7,!=2.1.0,>=1.6.2;python_version>='3.4'  # BSD
 openstackdocstheme>=1.18.1 # Apache-2.0
 reno>=2.5.0 # Apache-2.0

releasenotes/notes/drop-py-2-7-bfbdac2889ac051a.yaml

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

setup.cfg

@@ -6,6 +6,7 @@ description-file =
 author = OpenStack
 author-email = openstack-discuss@lists.openstack.org
 home-page = https://docs.openstack.org/neutron-vpnaas-dashboard/latest/
+python-requires = >=3.6
 classifier =
     Environment :: OpenStack
     Intended Audience :: Information Technology
@@ -13,8 +14,6 @@ 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

@@ -1,10 +1,12 @@
 [tox]
-envlist = py27,py37,py3-{dj111,dj22},pep8
-minversion = 2.3.2
+envlist = py37,py3-{dj111,dj22},pep8
+minversion = 3.1.1
 skipsdist = True
+ignore_basepython_conflict = True
 
 [testenv]
 usedevelop = True
+basepython = python3
 setenv = VIRTUAL_ENV={envdir}
          NOSE_WITH_OPENSTACK=1
          NOSE_OPENSTACK_COLOR=1
@@ -21,17 +23,14 @@ commands =
   python manage.py test {posargs} --settings=neutron_vpnaas_dashboard.test.settings
 
 [testenv:pep8]
-basepython = python3
 commands =
   flake8 {posargs}
   {envpython} {toxinidir}/manage.py extract_messages --module neutron_vpnaas_dashboard --verbosity 0 --check-only
 
 [testenv:venv]
-basepython = python3
 commands = {posargs}
 
 [testenv:cover]
-basepython = python3
 commands =
   coverage erase
   coverage run {toxinidir}/manage.py test neutron_vpnaas_dashboard --settings=neutron_vpnaas_dashboard.test.settings {posargs}
@@ -39,14 +38,12 @@ commands =
   coverage html --omit '.tox/cover/*' -d 'cover/htmlcov'
 
 [testenv:docs]
-basepython = python3
 deps =
   -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
   -r{toxinidir}/doc/requirements.txt
 commands = sphinx-build -W -b html doc/source doc/build/html
 
 [testenv:pdf-docs]
-basepython = python3
 envdir = {toxworkdir}/docs
 deps = {[testenv:docs]deps}
 whitelist_externals =
@@ -56,7 +53,6 @@ commands =
   make -C doc/build/pdf
 
 [testenv:releasenotes]
-basepython = python3
 deps =
   -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
   -r{toxinidir}/doc/requirements.txt
@@ -84,7 +80,6 @@ application-import-names = neutron_vpnaas_dashboard
 local-check-factory = horizon.hacking.checks.factory
 
 [testenv:lower-constraints]
-basepython = python3
 deps =
   -c{toxinidir}/lower-constraints.txt
   -r{toxinidir}/test-requirements.txt