Few python3 (and 3.6) compatibility improvements

- devstack plugin: run manage.py using $PYTHON (defined by devstack,
  it points to the Python interpreter used by DevStack;
- add an explicit envlist for py36;
- add the classifier for Python 3.6 to setup.cfg;
- bump the minumum tox version to 2.0, which is the de-facto
  minimum version.

Change-Id: I2bce1562b9ac49abf2e80efd3d6df392e40328b1

devstack/plugin.sh

@@ -12,7 +12,7 @@ function configure_sahara_dashboard {
     # NOTE: If locale directory does not exist, compilemessages will fail,
     # so check for an existence of locale directory is required.
     if [ -d ${SAHARA_DASH_DIR}/sahara_dashboard/locale ]; then
-        (cd ${SAHARA_DASH_DIR}/sahara_dashboard; DJANGO_SETTINGS_MODULE=openstack_dashboard.settings ../manage.py compilemessages)
+        (cd ${SAHARA_DASH_DIR}/sahara_dashboard; DJANGO_SETTINGS_MODULE=openstack_dashboard.settings $PYTHON ../manage.py compilemessages)
     fi
 }
 

setup.cfg

@@ -17,6 +17,7 @@ classifier =
     Programming Language :: Python :: 2.7
     Programming Language :: Python :: 3
     Programming Language :: Python :: 3.5
+    Programming Language :: Python :: 3.6
 
 [files]
 packages =

tox.ini

@@ -1,6 +1,6 @@
 [tox]
-minversion = 1.6
-envlist = py35,py27,pep8,py27dj18
+minversion = 2.0
+envlist = py36,py35,py27,pep8,py27dj18
 skipsdist = True
 
 [testenv]