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

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

Trove 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://governance.openstack.org/tc/goals/selected/ussuri/drop-py27.html

Change-Id: I6b448747c873bfc9c0138c0f7e3ca67ddce02dee

.zuul.yaml

@@ -3,8 +3,7 @@
       - check-requirements
       - openstack-cover-jobs
       - openstack-lower-constraints-jobs
-      - openstack-python-jobs
-      - openstack-python3-train-jobs
+      - openstack-python3-ussuri-jobs
       - periodic-stable-jobs
       - publish-openstack-docs-pti
       - release-notes-jobs-python3
@@ -113,6 +112,7 @@
         SERVICE_HOST: ''
         HOST_IP: ''
         VNCSERVER_PROXYCLIENT_ADDRESS: 127.0.0.1
+        USE_PYTHON3: True
     run: playbooks/trove-devstack-base.yaml
     irrelevant-files:
       - ^.*\.rst$
@@ -125,7 +125,7 @@
 
 - job:
     name: trove-fakemodetests-base
-    parent: openstack-tox-py27
+    parent: openstack-tox-py36
     abstract: true
     irrelevant-files:
       - ^.*\.rst$

playbooks/legacy/grenade-dsvm-trove/run.yaml

@@ -36,6 +36,7 @@
           export DEVSTACK_GATE_TROVE=1
           export TEMPEST_CONCURRENCY=2
           export BRANCH_OVERRIDE=default
+          export DEVSTACK_GATE_USE_PYTHON3=True
           if [ "$BRANCH_OVERRIDE" != "default" ] ; then
               export OVERRIDE_ZUUL_BRANCH=$BRANCH_OVERRIDE
           fi

releasenotes/notes/drop-py-2-7-010fe6df0c10352d.yaml

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

requirements.txt

@@ -43,7 +43,6 @@ oslo.messaging>=5.29.0 # Apache-2.0
 osprofiler>=1.4.0 # Apache-2.0
 oslo.log>=3.36.0 # Apache-2.0
 oslo.db>=4.27.0 # Apache-2.0
-enum34>=1.0.4;python_version=='2.7' or python_version=='2.6' or python_version=='3.3' # BSD
 xmltodict>=0.10.1 # MIT
 cryptography>=2.1.4  # BSD/Apache-2.0
 oslo.policy>=1.30.0 # Apache-2.0

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

@@ -1,9 +1,10 @@
 [tox]
-envlist = py27,py37,pep8,cover,api-ref,releasenotes,bandit,fakemodetests,pylint
+envlist = py37,pep8,cover,api-ref,releasenotes,bandit,fakemodetests,pylint
 minversion = 2.0
 skipsdist = True
 
 [testenv]
+basepython = python3
 setenv = VIRTUAL_ENV={envdir}
          PYTHONWARNINGS=default::DeprecationWarning
          OS_TEST_PATH=./trove/tests/unittests
@@ -29,21 +30,17 @@ whitelist_externals = find
 sitepackages = True
 
 [testenv:pep8]
-basepython = python3
 commands =
     flake8
     doc8 {posargs}
 
 [testenv:fakemodetests]
-basepython = python3
 commands = {envpython} run_tests.py
 
 [testenv:debug]
-basepython = python3
 commands = oslo_debug_helper {posargs}
 
 [testenv:cover]
-basepython = python3
 setenv =
   {[testenv]setenv}
   PYTHON=coverage run --source trove
@@ -56,7 +53,6 @@ commands =
      coverage report
 
 [testenv:venv]
-basepython = python3
 commands = {posargs}
 
 [doc8]
@@ -79,7 +75,6 @@ import_exceptions = trove.common.i18n
 local-check-factory = trove.hacking.checks.factory
 
 [testenv:api-ref]
-basepython = python3
 # This environment is called from CI scripts to test and publish
 # the API Ref to developer.openstack.org.
 commands =
@@ -87,41 +82,33 @@ commands =
   sphinx-build -W -b html -d api-ref/build/doctrees api-ref/source api-ref/build/html
 
 [testenv:releasenotes]
-basepython = python3
 commands = sphinx-build -a -E -W -d releasenotes/build/doctrees -b html releasenotes/source releasenotes/build/html
 
 [testenv:bandit]
-basepython = python3
 commands = bandit -r trove -n5 -x tests
 
 [testenv:bandit-baseline]
-basepython = python3
 envdir = {toxworkdir}/bandit
 commands = bandit-baseline -r trove -n5 -x tests -ii -ll
 
 [testenv:genpolicy]
-basepython = python3
 commands = oslopolicy-sample-generator --config-file=tools/trove-policy-generator.conf
 
 [testenv:pylint]
-basepython = python3
 deps = -r{toxinidir}/requirements.txt
        -r{toxinidir}/test-requirements.txt
 commands = python tools/trove-pylint.py {posargs:check}
 
 [testenv:docs]
-basepython = python3
 commands = sphinx-build -W -b html doc/source doc/build/html
 
 [testenv:lower-constraints]
-basepython = python3
 deps =
   -c{toxinidir}/lower-constraints.txt
   -r{toxinidir}/test-requirements.txt
   -r{toxinidir}/requirements.txt
 
 [testenv:trovestack]
-basepython = python3
 skip_install = True
 changedir = {toxinidir}/integration/scripts
 passenv = *