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

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

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: Ie48c796b6c83b42c85555d13a09f3b3ed96428f8
Sem-Ver: api-break

.zuul.yaml

@@ -27,11 +27,9 @@
 - project:
     templates:
       - check-requirements
-      - lib-forward-testing
       - lib-forward-testing-python3
       - openstack-lower-constraints-jobs
-      - openstack-python-jobs
+      - openstack-python3-ussuri-jobs
-      - openstack-python3-train-jobs
       - periodic-stable-jobs
       - publish-openstack-docs-pti
       - release-notes-jobs-python3

doc/requirements.txt

@@ -3,6 +3,5 @@
 # process, which may cause wedges in the gate later.
 openstackdocstheme>=1.20.0 # Apache-2.0
 reno>=2.5.0 # Apache-2.0
-sphinx>=1.8.0,<2.0.0;python_version=='2.7' # BSD
+sphinx>=1.8.0,!=2.1.0 # BSD
-sphinx>=1.8.0,!=2.1.0;python_version>='3.4' # BSD
 sphinxcontrib-apidoc>=0.2.0  # BSD

releasenotes/notes/drop-python27-support-7c1d29f348060147.yaml

@@ -0,0 +1,5 @@
+---
+upgrade:
+  - |
+    Support for Python 2.7 has been dropped. The minimum version of Python now
+    supported is Python 3.6.

setup.cfg

@@ -6,6 +6,7 @@ description-file =
 author = OpenStack
 author-email = openstack-discuss@lists.openstack.org
 home-page = https://docs.openstack.org/oslo.limit/latest/
+python-requires = >=3.6
 classifier =
     Environment :: OpenStack
     Intended Audience :: Information Technology
@@ -13,11 +14,11 @@ classifier =
     License :: OSI Approved :: Apache Software License
     Operating System :: POSIX :: Linux
     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
+    Programming Language :: Python :: 3 :: Only
+    Programming Language :: Python :: Implementation :: CPython
 
 [files]
 packages =
@@ -40,6 +41,3 @@ input_file = oslo_limit/locale/oslo_limit.pot
 keywords = _ gettext ngettext l_ lazy_gettext
 mapping_file = babel.cfg
 output_file = oslo_limit/locale/oslo_limit.pot
-
-[wheel]
-universal = true

setup.py

@@ -14,14 +14,6 @@
 # THIS FILE IS MANAGED BY THE GLOBAL REQUIREMENTS REPO - DO NOT EDIT
 import setuptools
 
-# In python < 2.7.4, a lazy loading of package `pbr` will break
-# setuptools if some other modules registered functions in `atexit`.
-# solution from: http://bugs.python.org/issue15881#msg170215
-try:
-    import multiprocessing  # noqa
-except ImportError:
-    pass
-
 setuptools.setup(
     setup_requires=['pbr>=2.0.0'],
     pbr=True)

tox.ini

@@ -1,7 +1,7 @@
 [tox]
-minversion = 3.1
+minversion = 3.1.1
-envlist = py27,py37,pep8,docs
+envlist = py37,pep8,docs
-ignore_basepython_conflict = True
+ignore_basepython_conflict = true
 
 [testenv]
 basepython = python3