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

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

masakari-monitors 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

Depends-On: https://review.opendev.org/#/c/693631/
Change-Id: Id27862284d34f6585881da39c0385cda91959b93

.zuul.yaml

@@ -2,7 +2,6 @@
     templates:
       - check-requirements
       - openstack-lower-constraints-jobs
-      - openstack-python-jobs
-      - openstack-python3-train-jobs
+      - openstack-python3-ussuri-jobs
       - publish-openstack-docs-pti
       - release-notes-jobs-python3

releasenotes/notes/drop-py-2-7-b28de816eac45468.yaml

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

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 +1,11 @@
 [tox]
-minversion = 2.0
-envlist = pep8,py27,py36,py37
+minversion = 3.1.1
+envlist = pep8,py36,py37
 skipsdist = True
+ignore_basepython_conflict = True
 
 [testenv]
+basepython = python3
 usedevelop = True
 install_command = pip install -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master} {opts} {packages}
 setenv = VIRTUAL_ENV={envdir}
@@ -23,11 +25,6 @@ commands =
   find . -type f -name "*.pyc" -delete
 passenv = http_proxy HTTP_PROXY https_proxy HTTPS_PROXY no_proxy NO_PROXY OS_DEBUG GENERATE_HASHES
 
-[testenv:py27]
-commands =
-    {[testenv]commands}
-    stestr run {posargs}
-
 [testenv:py36]
 basepython = python3.6
 commands =
@@ -41,19 +38,15 @@ commands =
     stestr run {posargs}
 
 [testenv:genconfig]
-basepython = python3
 commands = oslo-config-generator --config-file=etc/masakarimonitors/masakarimonitors-config-generator.conf
 
 [testenv:pep8]
-basepython = python3
 commands = flake8 {posargs}
 
 [testenv:venv]
-basepython = python3
 commands = {posargs}
 
 [testenv:cover]
-basepython = python3
 setenv =
     VIRTUAL_ENV={envdir}
     PYTHON=coverage run --source masakarimonitors --parallel-mode
@@ -64,19 +57,16 @@ commands =
     coverage xml -o cover/coverage.xml
 
 [testenv:docs]
-basepython = python3
 deps = -r{toxinidir}/doc/requirements.txt
 commands = python setup.py build_sphinx
 
 [testenv:releasenotes]
-basepython = python3
 deps = -r{toxinidir}/doc/requirements.txt
 commands =
   rm -fr releasenotes/build
   sphinx-build -a -E -W -d releasenotes/build/doctrees -b html releasenotes/source releasenotes/build/html
 
 [testenv:debug]
-basepython = python3
 commands = oslo_debug_helper {posargs}
 
 [flake8]
@@ -96,7 +86,6 @@ import_exceptions = masakarimonitors.i18n
 local-check-factory = masakarimonitors.hacking.checks.factory
 
 [testenv:lower-constraints]
-basepython = python3
 deps =
   -c{toxinidir}/lower-constraints.txt
   -r{toxinidir}/test-requirements.txt
@@ -109,7 +98,6 @@ deps =
 # separately, outside of the requirements files, and develop mode disabled
 # explicitly to avoid unnecessarily installing the checked-out repo too (this
 # further relies on "tox.skipsdist = True" above).
-basepython = python3
 deps = bindep
 commands = bindep test
 usedevelop = False