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

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

kuryr-tempest-plugin 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: I275bb0bae3e59b0abbea807f401361b201962e7f

doc/requirements.txt

@@ -1,7 +1,6 @@
 # The order of packages is significant, because pip processes them in the order
 # of appearance. Changing the order has an impact on the overall integration
 # process, which may cause wedges in the gate later.
-sphinx>=1.6.2,!=1.6.6,!=1.6.7,<2.0.0;python_version=='2.7'  # BSD
-sphinx>=1.6.2,!=1.6.6,!=1.6.7,!=2.1.0;python_version>='3.4'  # BSD
+sphinx>=1.6.2,!=1.6.6,!=1.6.7,!=2.1.0  # BSD
 openstackdocstheme>=1.18.1 # Apache-2.0
 reno>=2.5.0 # Apache-2.0

releasenotes/notes/drop-py-2-7-059b699f12500b28.yaml

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

setup.cfg

@@ -5,8 +5,9 @@ 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
     Environment :: OpenStack
     Intended Audience :: Information Technology
     Intended Audience :: System Administrators

tox.ini

@@ -1,9 +1,11 @@
 [tox]
-envlist = py35,py27,pep8,releasenotes
-minversion = 1.6
+envlist = py37,pep8,releasenotes
+minversion = 3.1.1
 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 =
@@ -15,17 +17,14 @@ commands = ostestr {posargs}
 passenv = http_proxy HTTP_PROXY https_proxy HTTPS_PROXY no_proxy NO_PROXY OS_*
 
 [testenv:venv]
-basepython = python3
 commands = {posargs}
 passenv = OS_*
 
 [testenv:docs]
-basepython = python3
 deps = -r{toxinidir}/doc/requirements.txt
 commands = sphinx-build -W -b html doc/source doc/build/html
 
 [testenv:pep8]
-basepython = python3
 commands =
     flake8 {posargs}