Drop old Python versions

Python 2.6 is dead since a while and we should move out from
Python 3.5 in favor of Python 3.6 and Python 3.7

Change-Id: I36ff0e1bc1db018bb7cce00a741682125aca4ac4

setup.cfg

@@ -14,9 +14,9 @@ classifier =
     Programming Language :: Python
     Programming Language :: Python :: 2
     Programming Language :: Python :: 2.7
-    Programming Language :: Python :: 2.6
     Programming Language :: Python :: 3
-    Programming Language :: Python :: 3.5
+    Programming Language :: Python :: 3.6
+    Programming Language :: Python :: 3.7
 
 [build_sphinx]
 all_files = 1

tox.ini

@@ -1,8 +1,9 @@
 [tox]
 minversion = 2.8.1
-envlist = py35,py27,pep8
+envlist = py27,py3,pep8
 
 [testenv]
+basepython = python3
 setenv = VIRTUAL_ENV={envdir}
          LANG=en_US.UTF-8
          LANGUAGE=en_US:en
@@ -20,11 +21,9 @@ commands = stestr run {posargs}
 sitepackages = True
 
 [testenv:pep8]
-basepython = python3
 whitelist_externals = bash
 
 [testenv:cover]
-basepython = python3
 setenv =
     {[testenv]setenv}
     PYTHON=coverage run --source pyghmi --parallel-mode
@@ -35,11 +34,9 @@ commands =
     coverage xml -o cover/coverage.xml
 
 [testenv:docs]
-basepython = python3
 commands = python setup.py build_sphinx
 
 [testenv:venv]
-basepython = python3
 commands = {posargs}
 
 [flake8]
@@ -50,7 +47,6 @@ show-source = true
 ignore = E731,E226,E123
 
 [testenv:lower-constraints]
-basepython = python3
 deps =
   -c{toxinidir}/lower-constraints.txt
   -r{toxinidir}/test-requirements.txt

zuul.d/project.yaml

@@ -1,3 +1,6 @@
 - project:
     templates:
+      - check-requirements
+      - openstack-python-jobs
+      - openstack-python3-ussuri-jobs
       - build-openstack-docs-pti