Cleanup py27 support

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

Change-Id: I21589f52dd5f888a3a93ae89857293466cf11695

setup.cfg

@@ -15,6 +15,7 @@ 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 :: 3.6
     Programming Language :: Python :: 3.7
@@ -24,18 +25,9 @@ classifier =
 packages =
     rally_openstack
 
-[global]
-setup-hooks =
-    pbr.hooks.setup_hook
-
 [entry_points]
 rally_plugins =
     path = rally_openstack
     options = rally_openstack.common.cfg.opts:list_opts
 oslo.config.opts =
     rally_openstack = rally_openstack.common.cfg.opts:list_opts
-
-[build_sphinx]
-all_files = 1
-build-dir = doc/build
-source-dir = doc/source

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

@@ -1,5 +1,5 @@
 [tox]
-minversion = 2.0
+minversion = 3.1.1
 skipsdist = True
 ignore_basepython_conflict = true
 envlist = py36,py37,py38,pep8
@@ -16,9 +16,10 @@ setenv = VIRTUAL_ENV={envdir}
 whitelist_externals = find
                       rm
                       make
-deps = -r{toxinidir}/requirements.txt
-       -r{toxinidir}/test-requirements.txt
-install_command = pip install -c ./upper-constraints.txt -U {opts} {packages}
+deps =
+  -c ./upper-constraints.txt
+  -r{toxinidir}/requirements.txt
+  -r{toxinidir}/test-requirements.txt
 usedevelop = True
 commands =
   find . -type f -name "*.pyc" -delete
@@ -65,7 +66,6 @@ commands =
 
 [testenv:requirements]
 deps = requests[security]
-install_command = pip install -U {opts} {packages}
 commands = python {toxinidir}/tests/ci/sync_requirements.py {posargs}
 
 [flake8]