[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: Ic8ebb5982135de079572cca300799a0d3c025ef3

.zuul.yaml

@@ -1,4 +1,3 @@
 - project:
     templates:
-      - openstack-python-jobs
-      - openstack-python3-train-jobs
+      - openstack-python3-ussuri-jobs

setup.cfg

@@ -7,6 +7,7 @@ description-file =
 author = OpenStack
 author-email = openstack-dev@lists.openstack.org
 home-page = http://www.openstack.org/
+python-requires = >=3.6
 classifier =
     Environment :: OpenStack
     Intended Audience :: Information Technology
@@ -14,8 +15,6 @@ 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
@@ -28,10 +27,6 @@ scripts =
     bin/heat-cfn
     bin/heat-watch
 
-[global]
-setup-hooks =
-    pbr.hooks.setup_hook
-
 [compile_catalog]
 directory = heat/locale
 domain = heat
@@ -45,8 +40,3 @@ input_file = heat/locale/heat.pot
 keywords = _ gettext ngettext l_ lazy_gettext
 mapping_file = babel.cfg
 output_file = heat/locale/heat.pot
-
-[build_sphinx]
-all_files = 1
-build-dir = doc/build
-source-dir = doc/source

setup.py

@@ -17,14 +17,6 @@
 # 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'],
     pbr=True)

tox.ini

@@ -1,15 +1,16 @@
 [tox]
-envlist = py27,py37,pep8
-minversion = 1.6
+envlist = py37,pep8
+ignore_basepython_conflict = true
+minversion = 3.1.0
 skipsdist = True
 
 [testenv]
+basepython = python3
 # Note the hash seed is set to 0 until heat can be tested with a
 # random hash seed successfully.
 setenv = VIRTUAL_ENV={envdir}
          PYTHONHASHSEED=0
 usedevelop = True
-install_command = pip install {opts} {packages}
 deps = -r{toxinidir}/requirements.txt
        -r{toxinidir}/test-requirements.txt
 commands =