Drop python 2 support and testing

This is part of Ussuri goal tracked for Neutron stadium at:
https://etherpad.openstack.org/p/neutron-train-zuulv3-py27drop

Change-Id: Idcbecc3ee3e2140cdff45a58cd4628064f17181f

.zuul.yaml

@@ -3,7 +3,6 @@
       - check-requirements
       - openstack-cover-jobs-neutron
       - openstack-lower-constraints-jobs-neutron
-      - openstack-python-jobs-neutron
       - openstack-python3-ussuri-jobs-neutron
       - periodic-stable-jobs-neutron
       - publish-openstack-docs-pti

releasenotes/notes/drop-py27-support-d83cd4daa0e37383.yaml

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

test-requirements.txt

@@ -9,7 +9,6 @@ flake8-import-order==0.12 # LGPLv3
 mock>=2.0.0 # BSD
 pylint==1.7.6 # GPLv2
 requests-mock>=1.2.0 # Apache-2.0
-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,>=1.6.2;python_version>='3.4' # BSD
 openstackdocstheme>=1.18.1 # Apache-2.0
 tempest>=17.1.0 # Apache-2.0

tox.ini

@@ -1,6 +1,6 @@
 [tox]
-envlist = py27,py37,pep8
-minversion = 2.3.2
+envlist = py36,py37,pep8
+minversion = 3.1.1
 skipsdist = True
 
 [testenv]
@@ -40,17 +40,12 @@ whitelist_externals =
 commands =
     pip install -q -e "git+https://opendev.org/openstack/neutron#egg=neutron"
 
-[testenv:py3-dev]
-basepython = python3
+[testenv:py-dev]
 commands =
     {[testenv:dev]commands}
-    pip freeze
-    stestr run {posargs}
-whitelist_externals =
-    stestr
+    {[testenv]commands}
 
 [testenv:dsvm-functional]
-basepython = python3
 setenv =
   OS_TEST_PATH=./neutron_vpnaas/tests/functional/openswan
   {[testenv:functional]setenv}
@@ -62,7 +57,6 @@ commands =
   stestr run {posargs}
 
 [testenv:dsvm-functional-sswan]
-basepython = python3
 setenv =
   OS_TEST_PATH=./neutron_vpnaas/tests/functional/strongswan
   {[testenv:functional]setenv}
@@ -74,11 +68,9 @@ commands =
   stestr run {posargs}
 
 [testenv:releasenotes]
-basepython = python3
 commands = sphinx-build -a -E -W -d releasenotes/build/doctrees -b html releasenotes/source releasenotes/build/html
 
 [testenv:pep8]
-basepython = python3
 commands =
   flake8
   pylint --rcfile=.pylintrc --output-format=colorized {posargs:neutron_vpnaas}
@@ -89,7 +81,6 @@ commands =
 whitelist_externals = sh
 
 [testenv:pep8-dev]
-basepython = python3
 deps =
     {[testenv]deps}
 commands =
@@ -100,7 +91,6 @@ commands =
 commands = python ./tools/check_i18n.py ./neutron-vpnaas ./tools/i18n_cfg.py
 
 [testenv:cover]
-basepython = python3
 setenv =
     {[testenv]setenv}
     PYTHON=coverage run --source neutron_vpnaas --parallel-mode
@@ -112,15 +102,12 @@ commands =
   coverage xml -o cover/coverage.xml
 
 [testenv:venv]
-basepython = python3
 commands = {posargs}
 
 [testenv:docs]
-basepython = python3
 commands = sphinx-build -W -a -b html doc/source doc/build/html
 
 [testenv:pdf-docs]
-basepython = python3
 envdir = {toxworkdir}/docs
 whitelist_externals =
   make
@@ -159,7 +146,6 @@ commands = {toxinidir}/tools/generate_config_file_samples.sh
 commands = oslopolicy-sample-generator --config-file=etc/oslo-policy-generator/policy.conf
 
 [testenv:lower-constraints]
-basepython = python3
 deps =
   -c{toxinidir}/lower-constraints.txt
   -r{toxinidir}/test-requirements.txt