[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: I02784f635368ad7cc5ffde7cc8a4f4367143da98

.zuul.yaml

@@ -1,10 +1,8 @@
 - project:
     templates:
       - check-requirements
-      - lib-forward-testing
       - lib-forward-testing-python3
       - openstack-lower-constraints-jobs
-      - openstack-python-jobs
       - openstack-python3-ussuri-jobs
       - periodic-stable-jobs
       - publish-openstack-docs-pti

doc/requirements.txt

@@ -3,8 +3,7 @@
 # process, which may cause wedges in the gate later.
 # These are needed for docs generation
 openstackdocstheme>=1.20.0 # 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
 reno>=2.5.0 # Apache-2.0
 
 mock>=2.0.0 # BSD

releasenotes/notes/drop-python27-support-a4d3707304c73df6.yaml

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

setup.cfg

@@ -6,6 +6,7 @@ summary = Oslo Rootwrap
 description-file =
     README.rst
 home-page = https://docs.openstack.org/oslo.rootwrap/latest/
+python-requires = >=3.6
 classifier =
     Development Status :: 4 - Beta
     Environment :: OpenStack
@@ -14,10 +15,11 @@ classifier =
     License :: OSI Approved :: Apache Software License
     Operating System :: OS Independent
     Programming Language :: Python
-    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 =

setup.py

@@ -16,14 +16,6 @@
 # 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
 envlist = py37,pep8
-ignore_basepython_conflict = True
+ignore_basepython_conflict = true
 
 [testenv]
 basepython = python3