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

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

monasca-statsd 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: I522d737c5202a7c7ac292547679b71fcddad3091

.zuul.yaml

@@ -3,11 +3,8 @@
       - check-requirements
       - openstack-cover-jobs
       - openstack-lower-constraints-jobs
-      - openstack-python-jobs
       - openstack-python3-ussuri-jobs
     check:
       jobs:
-        - monasca-tempest-python2-influxdb:
-            voting: false
         - monasca-tempest-python3-influxdb:
             voting: false

releasenotes/notes/drop-py-2-7-c9e3758f73d5cf29.yaml

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

setup.cfg

@@ -17,7 +17,6 @@ classifier =
     License :: OSI Approved :: Apache Software License
     Topic :: System :: Monitoring
     Programming Language :: Python
-    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
+envlist = py37,pep8,cover
 minversion = 2.5
 skipsdist = True
 
 [testenv]
+basepython = python3
 passenv = http_proxy
           HTTP_PROXY
           https_proxy
@@ -24,7 +25,6 @@ commands =
     stestr run {posargs}
 
 [testenv:cover]
-basepython = python3
 
 commands =
   coverage erase
@@ -32,32 +32,26 @@ commands =
   coverage report
 
 [testenv:debug]
-basepython = python3
 commands =
   oslo_debug_helper -t {toxinidir}/tests {posargs}
 
 [testenv:docs]
-basepython = python3
 commands =
   rm -rf doc/build
   python setup.py build_sphinx
 
 [testenv:bandit]
-basepython = python3
 commands = bandit -r monascastatsd -s B311 -n5 -x monascastatsd/tests
 
 [testenv:flake8]
-basepython = python3
 commands = flake8 monascastatsd
 
 [testenv:pep8]
-basepython = python3
 commands =
   {[testenv:flake8]commands}
   {[testenv:bandit]commands}
 
 [testenv:venv]
-basepython = python3
 commands = {posargs}
 
 [flake8]
@@ -66,7 +60,6 @@ exclude=.venv,.git,.tox,dist,*egg,build,docs,cover
 max-line-length = 100
 
 [testenv:lower-constraints]
-basepython = python3
 deps =
   -c{toxinidir}/lower-constraints.txt
   -r{toxinidir}/test-requirements.txt