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

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

sahara plugins do works with python 3 and the sahara core
does not support python 2.7 anymore anyway.

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: I5806dcb8f13e88a28c0b5e6de449efa9b95b6e73

.zuul.yaml

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

releasenotes/notes/drop-py2-7-75fab513d04abc88.yaml

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

setup.cfg

@@ -5,8 +5,6 @@ description-file = README.rst
 license = Apache Software License
 classifiers =
     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 +1,13 @@
 [tox]
-envlist = py27,py37,pep8
-minversion = 2.0
+envlist = py37,pep8
+minversion = 3.1.1
 skipsdist = True
+# this allows tox to infer the base python from the environment name
+# and override any basepython configured in this file
+ignore_basepython_conflict = true
 
 [testenv]
+basepython = python3
 usedevelop = True
 install_command = pip install {opts} {packages}
 setenv =
@@ -16,10 +20,6 @@ deps =
 commands = stestr run {posargs}
 passenv = http_proxy HTTP_PROXY https_proxy HTTPS_PROXY no_proxy NO_PROXY
 
-[testenv:debug-py27]
-basepython = python2.7
-commands = oslo_debug_helper -t sahara_plugin_ambari/tests/unit {posargs}
-
 [testenv:debug-py36]
 basepython = python3.6
 commands = oslo_debug_helper -t sahara_plugin_ambari/tests/unit {posargs}
@@ -29,7 +29,6 @@ basepython = python3.7
 commands = oslo_debug_helper -t sahara_plugin_ambari/tests/unit {posargs}
 
 [testenv:pep8]
-basepython = python3
 deps =
   -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
   -r{toxinidir}/requirements.txt
@@ -40,11 +39,9 @@ commands =
     doc8 doc/source
 
 [testenv:venv]
-basepython = python3
 commands = {posargs}
 
 [testenv:docs]
-basepython = python3
 deps =
   -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
   -r{toxinidir}/doc/requirements.txt
@@ -55,7 +52,6 @@ whitelist_externals =
     rm
 
 [testenv:pdf-docs]
-basepython = python3
 deps = {[testenv:docs]deps}
 commands =
     rm -rf doc/build/pdf
@@ -66,7 +62,6 @@ whitelist_externals =
     rm
 
 [testenv:releasenotes]
-basepython = python3
 deps =
   -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
   -r{toxinidir}/doc/requirements.txt
@@ -76,7 +71,6 @@ commands =
 whitelist_externals = rm
 
 [testenv:debug]
-basepython = python3
 # It runs tests from the specified dir (default is sahara_plugin_ambari/tests)
 # in interactive mode, so, you could use pbr for tests debug.
 # Example usage: tox -e debug -- -t sahara_plugin_ambari/tests/unit some.test.path
@@ -101,7 +95,6 @@ enable-extensions=H904,H106,H203,H204,H205
 ignore=E123,E226,E402,E731,W503
 
 [testenv:lower-constraints]
-basepython = python3
 deps =
   -c{toxinidir}/lower-constraints.txt
   -r{toxinidir}/test-requirements.txt