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: I93294c42a967ca19b9b04ead9cd636b52f1cc038

doc/requirements.txt

@@ -1,4 +1,4 @@
-sphinx!=1.6.6,!=1.6.7,>=1.6.2;python_version>='3.6'  # BSD
+sphinx!=1.6.6,!=1.6.7,>=1.6.2  # BSD
 sphinxcontrib-httpdomain>=1.3.0 # BSD
 sphinxcontrib-blockdiag>=1.5.4 # BSD
 reno>=2.5.0 # Apache-2.0

requirements.txt

@@ -7,7 +7,6 @@ cotyledon>=1.3.0 #Apache-2.0
 futurist>=1.8.0 # Apache-2.0
 jsonpath-rw-ext>=1.1.3 # Apache-2.0
 lxml>=3.4.1 # BSD
-monotonic>=0.6;python_version<'3.3' # Apache-2.0
 msgpack>=0.5.0 # Apache-2.0
 oslo.concurrency>=3.26.0 # Apache-2.0
 oslo.config>=5.2.0 # Apache-2.0

setup.cfg

@@ -7,6 +7,7 @@ description-file =
 author = OpenStack
 author-email = openstack-discuss@lists.openstack.org
 home-page = https://docs.openstack.org/ceilometer/latest/
+python-requires = >=3.6
 classifier =
     Environment :: OpenStack
     Intended Audience :: Information Technology
@@ -14,15 +15,13 @@ 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
     Topic :: System :: Monitoring
 
-[global]
-setup-hooks =
-    pbr.hooks.setup_hook
-
 [files]
 packages =
     ceilometer
@@ -239,9 +238,6 @@ oslo.config.opts =
     ceilometer = ceilometer.opts:list_opts
     ceilometer-auth = ceilometer.opts:list_keystoneauth_opts
 
-[build_sphinx]
-warning-is-error = False
-
 [extract_messages]
 keywords = _ gettext ngettext l_ lazy_gettext
 mapping_file = babel.cfg

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>=1.8'],
+    setup_requires=['pbr>=2.0.0'],
     pbr=True)