Cleanup Python 2.7 support

Make a few cleanups:
- Remove python 2.7 stanza from setup.py
- Add requires on python >= 3.6 to setup.cfg so that pypi and pip
  know about the requirement
- Remove ancient sections from setup.cfg
- Update requirements
- Remove unused import from conf.py

Change-Id: I87261d38992dedd87709ad8beff0bb533064e118

doc/requirements.txt

@@ -4,5 +4,5 @@
 # this is required for the docs build jobs
 openstackdocstheme>=1.20.0 # Apache-2.0
 os-api-ref>=1.4.0 # Apache-2.0
-sphinx!=1.6.6,!=1.6.7,!=2.1.0,>=1.6.5;python_version>='3.4'  # BSD
+sphinx!=1.6.6,!=1.6.7,!=2.1.0,>=1.6.5 # BSD
 reno>=2.5.0 # Apache-2.0

doc/source/conf.py

@@ -15,8 +15,6 @@ import os
 import sys
 
 
-from senlin.version import version_info as senlin_version
-
 sys.path.insert(0, os.path.abspath('../..'))
 
 BASE_DIR = os.path.dirname(os.path.abspath(__file__))

setup.cfg

@@ -6,6 +6,7 @@ description-file =
 author = OpenStack
 author-email = openstack-discuss@lists.openstack.org
 home-page = https://docs.openstack.org/senlin/latest/
+python-requires = >=3.6
 classifier =
     Environment :: OpenStack
     Intended Audience :: Information Technology
@@ -13,6 +14,7 @@ classifier =
     License :: OSI Approved :: Apache Software License
     Operating System :: POSIX :: Linux
     Programming Language :: Python
+    Programming Language :: Python :: 3 :: Only
     Programming Language :: Python :: 3
     Programming Language :: Python :: 3.6
     Programming Language :: Python :: 3.7
@@ -77,10 +79,6 @@ senlin.endpoints =
     heat = senlin.engine.notifications.heat_endpoint:HeatNotificationEndpoint
     nova = senlin.engine.notifications.nova_endpoint:NovaNotificationEndpoint
 
-[global]
-setup-hooks =
-    pbr.hooks.setup_hook
-
 [compile_catalog]
 directory = senlin/locale
 domain = senlin
@@ -94,9 +92,3 @@ input_file = senlin/locale/senlin.pot
 keywords = _ gettext ngettext l_ lazy_gettext
 mapping_file = babel.cfg
 output_file = senlin/locale/senlin.pot
-
-[build_sphinx]
-all_files = 1
-build-dir = doc/build
-source-dir = doc/source
-warning-is-error = 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)