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
- Remove old sections from setup.cfg: Wheel is not needed for python
  3 only repo

Change-Id: I92d21453d610ba7f90ae9b150e6a245ce0e709e6

setup.cfg

@@ -6,6 +6,7 @@ description-file =
 author = OpenStack
 author-email = openstack-discuss@lists.openstack.org
 home-page = https://docs.openstack.org/python-cinderclient/latest/
+python-requires = >=3.6
 classifier =
     Development Status :: 5 - Production/Stable
     Environment :: Console
@@ -19,11 +20,6 @@ classifier =
     Programming Language :: Python :: 3.6
     Programming Language :: Python :: 3.7
 
-
-[global]
-setup-hooks =
-    pbr.hooks.setup_hook
-
 [files]
 packages =
     cinderclient
@@ -34,9 +30,3 @@ console_scripts =
 
 keystoneauth1.plugin =
     noauth = cinderclient.contrib.noauth:CinderNoAuthLoader
-
-[upload_sphinx]
-upload-dir = doc/build/html
-
-[wheel]
-universal = 1

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)