Cleanup py27 support

This repo is now testing only with Python 3, so let's make
a few cleanups:
- Remove python 2.7 stanza from setup.py
- Remove obsolete sections from setup.cfg
- Remove install_command from tox.ini, the default is fine

Change-Id: I6639d4b8612f9f50c98da43aec24cc7dbdb87634

setup.cfg

@@ -12,16 +12,3 @@ classifier =
     Intended Audience :: System Administrators
     License :: OSI Approved :: Apache Software License
     Operating System :: POSIX :: Linux
-
-[egg_info]
-tag_build =
-tag_date = 0
-tag_svn_revision = 0
-
-[wheel]
-universal = 1
-
-[pbr]
-# Treat sphinx warnings as errors during the docs build; this helps us keep
-# the documentation clean.
-warnerrors = true

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'],
     pbr=True)

tox.ini

@@ -4,7 +4,6 @@ envlist = pep8,validate
 skipdist = True
 
 [testenv]
-install_command = pip install -U {opts} {packages}
 setenv =
    VIRTUAL_ENV={envdir}
 basepython = python3