[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

Remove cruft from setup.cfg.

Change-Id: Ic719c1f15120b68de97f0e20702b03baeb02f5e9

releasenotes/notes/drop-python-2-7-73d3113c69d724d6.yaml

@@ -0,0 +1,5 @@
+---
+upgrade:
+  - |
+    Python 2.7 support has been dropped. The minimum version of Python now
+    supported by openstackdocstheme 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/openstackdocstheme/latest/
+python-requires = >=3.6
 classifier =
     Environment :: OpenStack
     Intended Audience :: Information Technology
@@ -13,16 +14,13 @@ 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 :: 3.5
+    Programming Language :: Python :: 3.6
+    Programming Language :: Python :: 3.7
+    Programming Language :: Python :: 3 :: Only
+    Programming Language :: Python :: Implementation :: CPython
     Topic :: Documentation
 
-[global]
-setup-hooks =
-    pbr.hooks.setup_hook
-
 [files]
 packages =
     openstackdocstheme
@@ -30,6 +28,3 @@ scripts =
     bin/docstheme-build-translated.sh
     bin/docstheme-lang-display-name.py
     bin/docstheme-build-pdf
-
-[wheel]
-universal = 1

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

@@ -1,10 +1,11 @@
 [tox]
-minversion = 2.0
+minversion = 3.1.0
 envlist = pep8
+ignore_basepython_conflict = true
 
 [testenv]
+basepython = python3
 usedevelop = False
-install_command = pip install {opts} {packages}
 deps =
     -c{env:UPPER_CONSTRAINTS_FILE:https://opendev.org/openstack/requirements/raw/upper-constraints.txt}
     -r{toxinidir}/test-requirements.txt
@@ -16,22 +17,18 @@ whitelist_externals =
   make
 
 [testenv:pep8]
-basepython = python3
 commands =
     flake8 openstackdocstheme
 
 [testenv:venv]
-basepython = python3
 commands = {posargs}
 
 [testenv:docs]
-basepython = python3
 commands =
   rm -rf doc/build/html doc/build/doctrees
   sphinx-build -a -E -W -d doc/build/doctrees -b html doc/source doc/build/html
 
 [testenv:docs-starlingxdocs]
-basepython = python3
 envdir = {toxworkdir}/docs
 commands =
   rm -rf doc/build/html doc/build/doctrees
@@ -44,31 +41,26 @@ commands =
   sphinx-build -a -E -W -d api-ref/build/doctrees -b html api-ref/source api-ref/build/html
 
 [testenv:releasenotes]
-basepython = python3
 commands =
   rm -rf releasenotes/build
   sphinx-build -a -E -W -d releasenotes/build/doctrees -b html releasenotes/source releasenotes/build/html
 
 [testenv:releasenotes-starlingxdocs]
-basepython = python3
 commands =
   rm -rf releasenotes/build
   sphinx-build -a -E -W -d releasenotes/build/doctrees -b html -D html_theme=starlingxdocs releasenotes/source releasenotes/build/html
 
 [testenv:api-ref]
-basepython = python3
 commands =
   rm -rf api-ref/build
   sphinx-build -a -E -W -d api-ref/build/doctrees -b html api-ref/source api-ref/build/html
 
 [testenv:api-ref-starlingxdocs]
-basepython = python3
 commands =
   rm -rf api-ref/build
   sphinx-build -a -E -W -d api-ref/build/doctrees -b html -D html_theme=starlingxdocs api-ref/source api-ref/build/html
 
 [testenv:pdf-docs]
-basepython = python3
 envdir = {toxworkdir}/docs
 commands =
   rm -rf doc/build/pdf
@@ -76,7 +68,6 @@ commands =
   make -C doc/build/pdf
 
 [testenv:pdf-docs-starlingxdocs]
-basepython = python3
 envdir = {toxworkdir}/docs
 commands =
   rm -rf doc/build/pdf
@@ -88,7 +79,6 @@ commands =
 # system dependencies are missing, since it's used to tell you what system
 # dependencies are missing! This also means that bindep must be installed
 # separately, outside of the requirements files.
-basepython = python3
 deps = bindep
 commands = bindep test