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
- Update classifiers
- Update requirements, no need for python_version anymore

Change-Id: Ibcee6e71253fceb4c46442646a99f3b58e9df26d

setup.cfg

@@ -5,7 +5,8 @@ author-email = openstack-discuss@lists.openstack.org
 summary = Refresh system configuration
 description-file =
 	README.rst
-home-page = http://github.com/openstack/os-refresh-config
+home-page = http://opendev.org/openstack/os-refresh-config
+python-requires = >=3.6
 classifier =
 	Development Status :: 4 - Beta
 	Environment :: Console
@@ -15,6 +16,8 @@ classifier =
 	License :: OSI Approved :: Apache Software License
 	Operating System :: OS Independent
 	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
@@ -31,6 +34,3 @@ console_scripts =
 tag_build =
 tag_date = 0
 tag_svn_revision = 0
-
-[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

@@ -6,8 +6,7 @@ hacking!=0.13.0,<0.14,>=0.12.0 # Apache-2.0
 coverage!=4.4,>=4.0 # Apache-2.0
 fixtures>=3.0.0 # Apache-2.0/BSD
 python-subunit>=1.0.0 # Apache-2.0/BSD
-sphinx!=1.6.6,!=1.6.7,>=1.6.2,<2.0.0;python_version=='2.7' # BSD
-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
 stestr>=2.0.0 # Apache-2.0
 testscenarios>=0.4 # Apache-2.0/BSD
 testtools>=2.2.0 # MIT