Drop Python 2 Support

1. It's Ussuri. We can *finally* stop testing Python 2 [1]. Time to party.
We don't attempt any cleanup but simply stop testing with Python 2,
indicate that we only support Python 3 via 'setup.cfg' and remove any
Python 2 only dependencies.

This should free up a significant amount of resources from the gate and
let us start using Python 3 idioms in our code. Win-win.

2. Cleanup basepython from individual testenv sections

3. From this point on the codebase will be incompatible with python2

[1] https://governance.openstack.org/tc/resolutions/20180529-python2-deprecation-timeline.html#python2-deprecation-timeline

Change-Id: Ia08c363263aaa406d0bf55e10ce8258695387578

.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

doc/requirements.txt

@@ -1,8 +1,7 @@
 # The order of packages is significant, because pip processes them in the order
 # 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,>=1.6.2;python_version>='3.4'  # BSD
+sphinx!=1.6.6,!=1.6.7,>=1.6.2 # BSD
 sphinxcontrib-apidoc>=0.2.0  # BSD
 sphinxmark>=0.1.14 # Apache-2.0
 openstackdocstheme>=1.18.1 # Apache-2.0

releasenotes/notes/drop-python-2-7-73d3113c69d724c1.yaml

@@ -0,0 +1,5 @@
+---
+upgrade:
+  - |
+    Python 2.7 support has been dropped. The minimum version of Python now
+    supported by neutron-fwaas 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-fwaas/latest/
+python-requires = >=3.6
 classifier =
     Environment :: OpenStack
     Intended Audience :: Information Technology
@@ -16,6 +17,7 @@ classifier =
     Programming Language :: Python :: 3
     Programming Language :: Python :: 3.6
     Programming Language :: Python :: 3.7
+    Programming Language :: Python :: 3 :: Only
 
 [files]
 packages =

tox.ini

@@ -1,9 +1,10 @@
 [tox]
-envlist = py27,py37,pep8,pylint
-minversion = 2.0
+envlist = py37,pep8,pylint
+minversion = 3.1.1
 skipsdist = True
 
 [testenv]
+basepython = python3
 setenv = VIRTUAL_ENV={envdir}
          PYTHONWARNINGS=default::DeprecationWarning
 usedevelop = True
@@ -24,7 +25,6 @@ setenv = OS_TEST_TIMEOUT=180
 commands = false
 
 [testenv:dsvm]
-basepython = python3
 # Fake job to define environment variables shared between dsvm jobs
 setenv = OS_SUDO_TESTING=1
          OS_ROOTWRAP_CMD=sudo {envdir}/bin/neutron-rootwrap {envdir}/etc/neutron/rootwrap.conf
@@ -34,7 +34,6 @@ setenv = OS_SUDO_TESTING=1
 commands = false
 
 [testenv:functional]
-basepython = python3
 setenv = {[testenv]setenv}
          {[testenv:common]setenv}
          OS_TEST_PATH=./neutron_fwaas/tests/functional
@@ -43,7 +42,6 @@ commands =
   stestr run {posargs}
 
 [testenv:dsvm-fullstack]
-basepython = python3
 setenv = {[testenv]setenv}
          {[testenv:common]setenv}
          {[testenv:dsvm]setenv}
@@ -57,7 +55,6 @@ commands =
 
 
 [testenv:api]
-basepython = python3
 sitepackages=True
 setenv =
  OS_TEST_PATH=./neutron_fwaas/tests/tempest_plugin/tests/api/
@@ -67,7 +64,6 @@ commands =
   stestr run {posargs}
 
 [testenv:scenario]
-basepython = python3
 sitepackages=True
 setenv =
  OS_TEST_PATH=./neutron_fwaas/tests/tempest_plugin/tests/scenario/
@@ -77,7 +73,6 @@ commands =
   stestr run {posargs}
 
 [testenv:dsvm-functional]
-basepython = python3
 setenv =
   OS_TEST_PATH=./neutron_fwaas/tests/functional
   OS_SUDO_TESTING=1
@@ -94,12 +89,10 @@ commands =
   stestr run {posargs}
 
 [testenv:releasenotes]
-basepython = python3
 deps = -r{toxinidir}/doc/requirements.txt
 commands = sphinx-build -a -E -W -d releasenotes/build/doctrees -b html releasenotes/source releasenotes/build/html
 
 [testenv:pep8]
-basepython = python3
 commands =
   flake8
   doc8 {posargs}
@@ -110,7 +103,6 @@ commands =
 whitelist_externals = sh
 
 [testenv:cover]
-basepython = python3
 setenv = VIRTUAL_ENV={envdir}
          LANGUAGE=en_US
          PYTHON=coverage run --source neutron_fwaas --omit='*tests*' --parallel-mode
@@ -123,12 +115,10 @@ commands =
   coverage xml -o cover/coverage.xml
 
 [testenv:venv]
-basepython = python3
 commands = {posargs}
 deps = -r{toxinidir}/doc/requirements.txt
 
 [testenv:docs]
-basepython = python3
 deps = -r{toxinidir}/doc/requirements.txt
 whitelist_externals =
   rm
@@ -137,7 +127,6 @@ 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 =
@@ -179,7 +168,6 @@ exclude = .venv,.git,.tox,dist,doc,*lib/python*,.tmp,*egg,build,tools,.ropeproje
 import-order-style = pep8
 
 [testenv:pylint]
-basepython = python3
 deps =
   {[testenv]deps}
   pylint
@@ -191,14 +179,12 @@ import_exceptions = neutron_fwaas._i18n
 local-check-factory = neutron_lib.hacking.checks.factory
 
 [testenv:genconfig]
-basepython = python3
 commands = {toxinidir}/tools/generate_config_file_samples.sh
 
 [testenv:genpolicy]
 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
@@ -211,7 +197,6 @@ commands =
     pip install -q -e "git+https://git.openstack.org/openstack/neutron#egg=neutron"
 
 [testenv:py3-dev]
-basepython = python3
 commands =
     {[testenv:dev]commands}
     {[testenv]commands}