Enable pep8 check for config.py in doc

Directory doc is excluded from pep8 check in tox.ini, since we
modified file doc/source/config.py, we should enable the check.

Change-Id: I057f1e6cb1c5f9a6a07043056078e4475f66f288

doc/source/conf.py

@@ -1,4 +1,15 @@
 # -*- coding: utf-8 -*-
+# Licensed under the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License. You may obtain
+# a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations
+# under the License.
 #
 # python-novaclient documentation build configuration file, created by
 # sphinx-quickstart on Sun Dec  6 14:19:25 2009.

tox.ini

@@ -30,4 +30,4 @@ downloadcache = ~/cache/pip
 [flake8]
 ignore = E12,F841,F811,F821,H302,H404
 show-source = True
-exclude=.venv,.git,.tox,dist,doc,*openstack/common*,*lib/python*,*egg,build
+exclude=.venv,.git,.tox,dist,*openstack/common*,*lib/python*,*egg,build