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 obsolete sections from setup.cfg:
  * Wheel is not needed for python 3 only repo
  * Some other sections are obsolete
- Update classifiers
- Update requirements, no need for python_version anymore

Change-Id: I95fb0ca759471f7ad7189a7d54c1dac2cc018fc4

setup.cfg

@@ -3,24 +3,23 @@ name = monasca-persister
 author = OpenStack
 author-email = openstack-discuss@lists.openstack.org
 summary = Moves metrics and alarm state transitions from the Message Queue to the Metrics and Alarms database.
+python-requires = >=3.6
 classifier=
   Development Status :: 5 - Production/Stable
   License :: OSI Approved :: Apache Software License
   Topic :: System :: Monitoring
   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
 
 keywords = openstack monitoring storage
 description-file = README.rst
-home-page = https://github.com/openstack/monasca-persister
+home-page = https://opendev.org/openstack/monasca-persister
 license = Apache
 
-[global]
-setup-hooks =
-    pbr.hooks.setup_hook
-
 [entry_points]
 console_scripts =
     monasca-persister = monasca_persister.persister:main
@@ -37,8 +36,7 @@ data_files =
 
 [extras]
 influxdb =
-  influxdb!=5.2.0,!=5.2.1,!=5.2.2,!=5.2.3,>=2.9.2;python_version<'3.0'  # MIT
+  influxdb>=2.9.2 # MIT
-  influxdb>=2.9.2;python_version>='3.0'  # MIT
 cassandra =
   cassandra-driver>=3.11.0 # Apache-2.0
 elasticsearch =
@@ -46,7 +44,3 @@ elasticsearch =
 
 [pbr]
 autodoc_index_modules = True
-
-[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)

test-requirements.txt

@@ -13,6 +13,6 @@ pycodestyle>=2.5.0 # MIT
 cassandra-driver>=3.11.0
 
 # release notes
-sphinx!=1.6.6,!=1.6.7,!=2.1.0,>=1.6.2;python_version>='3.4' # BSD
+sphinx!=1.6.6,!=1.6.7,!=2.1.0,>=1.6.2 # BSD
 reno>=2.5.0 # Apache-2.0
 openstackdocstheme>=1.20.0 # Apache-2.0