Stop testing python2.7

Train was the last release supporting python2. Let's rip the bandaid
off.

Change-Id: I842cf731fbad0dae72cf902366655eb7b4f8ca1b

releasenotes/notes/drop-py2-76af844b0b952a91.yaml

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

setup.cfg

@@ -15,8 +15,6 @@ classifier =
 	License :: OSI Approved :: Apache Software License
 	Operating System :: OS Independent
 	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 +1,14 @@
 [tox]
-minversion = 2.0
+minversion = 3.1.0
 skipsdist = True
-envlist = py27,py37,pep8
+envlist = py37,pep8
+skip_missing_interpreters = 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
 deps =
        -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
@@ -17,11 +22,9 @@ commands =
 sitepackages = True
 
 [testenv:pep8]
-basepython = python3
 commands = flake8
 
 [testenv:cover]
-basepython = python3
 setenv =
     PYTHON=coverage run --source os_refresh_config --parallel-mode
 commands =
@@ -31,7 +34,6 @@ commands =
     coverage xml -o cover/coverage.xml
 
 [testenv:venv]
-basepython = python3
 commands = {posargs}
 
 [flake8]

zuul.d/layout.yaml

@@ -2,6 +2,5 @@
     templates:
       - check-requirements
       - openstack-cover-jobs
-      - openstack-python-jobs
       - openstack-python3-ussuri-jobs
       - tripleo-multinode-container-minimal