Cleanup py27 support

This repo is now testing only with Python 3, so let's 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 obsolete sections from setup.cfg
- Update classifiers
- Use newer openstackdocstheme, Sphinx, os-api-ref versions,
  remove unused mock requirement

Change-Id: If7db350ea55a5edf7055ce049d27d9412b0e40bc

doc/requirements.txt

@@ -1,10 +1,9 @@
 # The order of packages is significant, because pip processes them in the order
 # of appearance. Changing the order has an impact on the overall integration
 # process, which may cause wedges in the gate later.
-openstackdocstheme>=1.20.0 # Apache-2.0
+openstackdocstheme>=2.0.0 # Apache-2.0
 reno>=2.5.0 # Apache-2.0
-sphinx!=1.6.6,!=1.6.7,!=2.1.0,>=1.6.3  # BSD
-os-api-ref>=1.4.0 # Apache-2.0
+sphinx!=1.6.6,!=1.6.7,!=2.1.0,>=2.0.0  # BSD
+os-api-ref>=1.5.0 # Apache-2.0
 sphinxcontrib-apidoc>=0.2.0  # BSD
 sphinx-feature-classification>=0.1.0 # Apache 2.0
-mock>=2.0.0 # BSD

lower-constraints.txt

@@ -63,7 +63,7 @@ netaddr==0.7.19
 netifaces==0.10.6
 networkx==1.11
 oauth2client==1.5.0
-openstackdocstheme==1.20.0
+openstackdocstheme==2.0.0
 os-api-ref==1.4.0
 os-brick==2.2.0
 os-client-config==1.29.0
@@ -134,7 +134,7 @@ rtslib-fb==2.1.65
 six==1.10.0
 smmap2==2.0.3
 snowballstemmer==1.2.1
-Sphinx==1.6.5
+Sphinx==2.0.0
 sphinx-feature-classification==0.1.0
 sphinxcontrib-websupport==1.0.1
 sqlalchemy-migrate==0.11.0

setup.cfg

@@ -6,6 +6,7 @@ description-file =
 author = OpenStack
 author-email = openstack-discuss@lists.openstack.org
 home-page = https://docs.openstack.org/cinder/latest/
+python-requires = >=3.6
 classifier =
     Environment :: OpenStack
     Intended Audience :: Information Technology
@@ -13,14 +14,12 @@ 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
 
-[global]
-setup-hooks =
-    pbr.hooks.setup_hook
-
 [files]
 data_files =
     etc/cinder =
@@ -75,12 +74,6 @@ wsgi_scripts =
 cinder.database.migration_backend =
     sqlalchemy = oslo_db.sqlalchemy.migration
 
-
-[egg_info]
-tag_build =
-tag_date = 0
-tag_svn_revision = 0
-
 [compile_catalog]
 directory = cinder/locale
 domain = cinder

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)