Sync Sphinx requirement

1. Sync sphinx dependency with global requirements. It caps python 2 since
sphinx 2.0 no longer supports Python 2.7.
2. Update some URLs to latest

Change-Id: I1bb1b6861f804f3a28d863bcab795ed39819d3aa

CONTRIBUTING.rst

@@ -2,13 +2,13 @@ If you would like to contribute to the development of OpenStack,
 you must follow the steps in the "If you're a developer, start here"
 section of this page:
 
-   http://wiki.openstack.org/HowToContribute
+   https://docs.openstack.org/infra/manual/developers.html
 
 Once those steps have been completed, changes to OpenStack
 should be submitted for review via the Gerrit tool, following
 the workflow documented at:
 
-   http://wiki.openstack.org/GerritWorkflow
+   https://docs.openstack.org/infra/manual/developers.html#development-workflow
 
 Pull requests submitted through GitHub will be ignored.
 

README.rst

@@ -33,7 +33,7 @@ installed locally already. In this case, you can interact with the testr
 command directly. Running `testr run` will run the entire test suite. `testr
 run --parallel` will run it in parallel (this is the default incantation tox
 uses.) More information about testr can be found at:
-http://wiki.openstack.org/testr
+https://wiki.openstack.org/wiki/Testr
 
 Basic Usage
 -----------

doc/source/contributor/index.rst

@@ -1,5 +1,5 @@
-==============
- Contributing
-==============
+============
+Contributing
+============
 
 .. include:: ../../../CONTRIBUTING.rst

test-requirements.txt

@@ -14,6 +14,7 @@ testtools>=2.2.0 # MIT
 six>=1.10.0 # MIT
 
 # this is required for the docs build jobs
-sphinx!=1.6.6,!=1.6.7,>=1.6.5 # BSD
+sphinx!=1.6.6,!=1.6.7,>=1.6.5,<2.0.0;python_version=='2.7'  # BSD
+sphinx!=1.6.6,!=1.6.7,>=1.6.5;python_version>='3.4'  # BSD
 openstackdocstheme>=1.18.1 # Apache-2.0