Cleanup py27 support

Make a few cleanups:
- Remove python 2.7 stanza from setup.py
- Remove obsolete sections from setup.cfg:
  * Wheel is not needed for python 3 only repo
- Update classifiers

Change-Id: I391f53925c1b20d2e8ad1685358c81dcbdaaf34c

setup.cfg

@@ -14,6 +14,8 @@ 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
@@ -26,6 +28,3 @@ data_files =
 scripts =
     bin/doc-tools-check-languages
     bin/doc-tools-build-rst
-
-[bdist_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)