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: Ia739f33b3db2c15a8c2eb6143134587f31591cfd

requirements.txt

@@ -37,7 +37,7 @@ sqlalchemy-migrate>=0.11.0 # Apache-2.0
 stevedore>=1.20.0 # Apache-2.0
 suds-jurko>=0.6 # LGPLv3+
 WebOb>=1.7.1 # MIT
-dnspython3!=1.13.0,!=1.14.0,>=1.12.0;python_version>='3.0' # http://www.dnspython.org/LICENSE
+dnspython3!=1.13.0,!=1.14.0,>=1.12.0 # http://www.dnspython.org/LICENSE
 oslo.db>=4.27.0 # Apache-2.0
 oslo.i18n>=3.15.3 # Apache-2.0
 oslo.context>=2.19.2 # Apache-2.0

setup.cfg

@@ -6,6 +6,7 @@ description-file =
 author = OpenStack
 author-email = openstack-discuss@lists.openstack.org
 home-page = https://docs.openstack.org/designate/latest/
+python-requires = >=3.6
 classifier =
     Environment :: OpenStack
     Environment :: No Input/Output (Daemon)
@@ -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 :: Internet :: Name Service (DNS)
 
-[global]
-setup-hooks =
-    pbr.hooks.setup_hook
-
 [files]
 packages =
     designate
@@ -147,6 +146,3 @@ input_file = designate/locale/designate.pot
 keywords = _ gettext ngettext l_ lazy_gettext
 mapping_file = babel.cfg
 output_file = designate/locale/designate.pot
-
-[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)