Cleanup py27 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
- Update classifiers
- Update requirements, no need for python_version anymore
- Remove html_last_updated_fmt from conf.py since it's set
  by newer openstackdocstheme, update requirement of openstackdocstheme.

Change-Id: I13f089de86ce3eb30770c91ee5372652e40fb52b

doc/requirements.txt

@@ -1,6 +1,6 @@
-sphinx>=1.8.0,!=2.1.0;python_version>='3.4' # BSD
+sphinx>=1.8.0,!=2.1.0 # BSD
 sphinxcontrib-apidoc>=0.2.0  # BSD
-openstackdocstheme>=1.18.1 # Apache-2.0
+openstackdocstheme>=1.32.1 # Apache-2.0
 
 # releasenotes
 reno>=2.5.0 # Apache-2.0

doc/source/conf.py

@@ -37,7 +37,6 @@ apidoc_excluded_paths = ['tests/*']
 
 apidoc_separate_modules = True
 
-# Must set this variable to include year, month, day, hours, and minutes.
 html_last_updated_fmt = '%Y-%m-%d %H:%M'
 
 # autodoc generation is a bit aggressive and a nuisance when doing heavy

lower-constraints.txt

@@ -26,7 +26,7 @@ msgpack-python==0.4.0
 msgpack==0.5.6
 netaddr==0.7.19
 netifaces==0.10.6
-openstackdocstheme==1.18.1
+openstackdocstheme==1.32.1
 oslo.config==5.2.0
 oslo.context==2.20.0
 oslo.i18n==3.15.3

setup.cfg

@@ -6,6 +6,7 @@ description-file =
 author = OpenStack
 author-email = openstack-discuss@lists.openstack.org
 home-page = https://docs.openstack.org/python-congressclient/latest/
+python-requires = >=3.6
 classifier =
     Environment :: OpenStack
     Intended Audience :: Information Technology
@@ -13,6 +14,8 @@ classifier =
     License :: OSI Approved :: Apache Software License
     Operating System :: POSIX :: Linux
     Programming Language :: Python
+    Programming Language :: Python :: Implementation :: CPython
+    Programming Language :: Python :: 3 :: Only
     Programming Language :: Python :: 3
     Programming Language :: Python :: 3.6
     Programming Language :: Python :: 3.7

setup.py

@@ -13,17 +13,8 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-# 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)