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

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

Tricircle 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: Ia1352479bf3148ca68c432acf30cd55290d8bd3e

.zuul.yaml

@@ -1,15 +1,3 @@
-- job:
-    name: tricircle-functional
-    parent: legacy-dsvm-base
-    run: playbooks/tricircle-dsvm-functional/run.yaml
-    post-run: playbooks/tricircle-dsvm-functional/post.yaml
-    timeout: 7800
-    required-projects:
-      - openstack/devstack-gate
-      - openstack/tricircle
-      - openstack/neutron
-      - openstack/networking-sfc
-
 - job:
     name: tricircle-functional-python3
     parent: legacy-dsvm-base
@@ -53,7 +41,6 @@
 
 - project:
     templates:
-      - openstack-python-jobs-neutron
       - openstack-python3-ussuri-jobs-neutron
       - openstack-python3-ussuri-jobs
       - check-requirements
@@ -67,14 +54,10 @@
             required-projects:
               - openstack/neutron
               - openstack/networking-sfc
-        - openstack-tox-py27:
-            required-projects:
-              - openstack/neutron
         - openstack-tox-py36:
             required-projects:
               - openstack/neutron
               - openstack/networking-sfc
-        - tricircle-functional
         - tricircle-functional-python3
         - tricircle-multiregion
     gate:
@@ -84,12 +67,8 @@
             required-projects:
               - openstack/neutron
               - openstack/networking-sfc
-        - openstack-tox-py27:
-            required-projects:
-              - openstack/neutron
         - openstack-tox-py36:
             required-projects:
               - openstack/neutron
               - openstack/networking-sfc
-        - tricircle-functional
         - tricircle-multiregion

playbooks/tricircle-dsvm-multiregion/run.yaml

@@ -32,6 +32,7 @@
           export PROJECTS="openstack/networking-sfc $PROJECTS"
           export DEVSTACK_GATE_CONFIGDRIVE=0
           export DEVSTACK_GATE_NEUTRON=1
+          export DEVSTACK_GATE_USE_PYTHON3=True
           export DEVSTACK_GATE_TEMPEST=0
           export DEVSTACK_GATE_TEMPEST_ALL_PLUGINS=0
           export DEVSTACK_GATE_TEMPEST_REGEX="tricircle.tempestplugin"

releasenotes/notes/drop-py-2-7-afccd2f6bec9dfb5.yaml

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

setup.cfg

@@ -12,8 +12,6 @@ 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 +1,11 @@
 [tox]
-minversion = 2.0
+minversion = 3.1.1
-envlist = py27,py37,pypy,pep8
+envlist = py37,pypy,pep8
 skipsdist = True
+ignore_basepython_conflict = True
 
 [testenv]
+basepython = python3
 setenv = VIRTUAL_ENV={envdir}
          PYTHONWARNINGS=default::DeprecationWarning
 passenv = TRACE_FAILONLY GENERATE_HASHES http_proxy HTTP_PROXY https_proxy HTTPS_PROXY no_proxy NO_PROXY
@@ -19,50 +21,41 @@ commands =
  stestr slowest
 
 [testenv:releasenotes]
-basepython = python3
 commands = sphinx-build -a -W -E -d releasenotes/build/doctrees -b html releasenotes/source releasenotes/build/html
 
 [testenv:pep8]
-basepython = python3
 deps =
     -r{toxinidir}/test-requirements.txt
 commands = flake8
 
 [testenv:venv]
-basepython = python3
 commands = {posargs}
 
 [testenv:cover]
-basepython = python3
 commands =
   python setup.py testr --coverage --testr-args='{posargs}'
   coverage report --fail-under=70 --skip-covered
 
 [testenv:genconfig]
-basepython = python3
 deps =
     -r{toxinidir}/test-requirements.txt
 commands = oslo-config-generator --config-file=etc/api-cfg-gen.conf
            oslo-config-generator --config-file=etc/xjob-cfg-gen.conf
 
 [testenv:genpolicy]
-basepython = python3
 deps =
     -r{toxinidir}/test-requirements.txt
 commands = oslopolicy-sample-generator --config-file=etc/policy-generator.conf
 
 [testenv:docs]
-basepython = python3
 deps =
     -r{toxinidir}/test-requirements.txt
 commands = python setup.py build_sphinx
 
 [testenv:debug]
-basepython = python3
 commands = oslo_debug_helper {posargs}
 
 [testenv:lower-constraints]
-basepython = python3
 deps =
   -c{toxinidir}/lower-constraints.txt
   -r{toxinidir}/test-requirements.txt
@@ -87,12 +80,6 @@ commands =
     pip install -q -e "git+https://opendev.org/openstack/networking-sfc#egg=networking_sfc"
     pip install -q -e "git+https://opendev.org/openstack/neutron#egg=neutron"
 
-[testenv:py27-dev]
-basepython = python2.7
-commands =
-    {[testenv:dev]commands}
-    {[testenv]commands}
-
 [testenv:py3-dev]
 basepython = python3
 commands =