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: Ie23843938154df3a969b7755e1ca82d6b672c580

setup.cfg

@@ -4,13 +4,14 @@ maintainer = OpenStack
 maintainer_email = openstack-discuss@lists.openstack.org
 description-file = README.rst
 summary = Monitoring agent for gathering metrics and sending them to the Monasca API.
-home-page = https://github.com/openstack/monasca-agent
+home-page = https://opendev.org/openstack/monasca-agent
 keywords=
     openstack
     monitoring
 license = Apache-2
 include_package_data = True
 test_suite = nose.collector
+python-requires = >=3.6
 classifier=
     Development Status :: 5 - Production/Stable
     License :: OSI Approved :: Apache Software License
@@ -19,6 +20,8 @@ classifier=
     Programming Language :: Python :: 3
     Programming Language :: Python :: 3.6
     Programming Language :: Python :: 3.7
+    Programming Language :: Python :: 3 :: Only
+    Programming Language :: Python :: Implementation :: CPython
 
 [files]
 packages =
@@ -54,8 +57,6 @@ influxdb_relay =
   toml
 kafka_plugin =
   monasca-common>=1.4.0 # Apache-2.0
-kubernetes_api =
-   ipaddress>=1.0.16 #python_version<'3.3'  # PSF
 libvirt =
   libvirt-python>=3.5.0 # LGPLv2+
   python-novaclient>=9.1.0 # Apache-2.0
@@ -69,18 +70,3 @@ swift_handoffs =
   swift >= 2.0.0 # Apache-2.0
 cert_file_check =
   cryptography>=2.1 # BSD/Apache-2.0
-
-[global]
-setup-hooks =
-    pbr.hooks.setup_hook
-
-[pbr]
-autodoc_index_modules = True
-
-[wheel]
-universal = 1
-
-[egg_info]
-tag_build =
-tag_date = 0
-tag_svn_revision = 0

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)