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
3. Remove the unnecessary space

Change-Id: I5464be9e055feecd80918f691448acf5f100e701

README.rst

@@ -6,7 +6,7 @@ wide-range of disk images, filesystem images and ramdisk images for
 use with OpenStack.
 
 This repository has the core functionality for building such images,
-both virtual and bare metal.  Images are composed using `elements`;
+both virtual and bare metal. Images are composed using `elements`;
 while fundamental elements are provided here, individual projects have
 the flexibility to customise the image build with their own elements.
 
@@ -17,9 +17,9 @@ For example::
 will create a bootable Ubuntu Trusty based ``qcow2`` image.
 
 ``diskimage-builder`` is useful to anyone looking to produce
-customised images for deployment into clouds.  These tools are the
+customised images for deployment into clouds. These tools are the
 components of `TripleO <https://wiki.openstack.org/wiki/TripleO>`__
-that are responsible for building disk images.  They are also used
+that are responsible for building disk images. They are also used
 extensively to build images for testing OpenStack itself, particularly
 with `nodepool
 <https://docs.openstack.org/infra/system-config/nodepool.html>`__.

diskimage_builder/elements/pypi/README.rst

@@ -1,6 +1,8 @@
 ====
 pypi
 ====
+
+====================
 Inject a PyPI mirror
 ====================
 
@@ -57,5 +59,5 @@ the upstream can't be contacted.
 
 Note that this process only has the server running temporarily; see
 [Quickstart: Permanent install on
-server/laptop](http://doc.devpi.net/latest/quickstart-server.html) guide from
+server/laptop](https://devpi.net/docs/devpi/devpi/latest/+d/quickstart-server.html)
-the devpi developers for more information on a more permanent setup.
+guide from the devpi developers for more information on a more permanent setup.

test-requirements.txt

@@ -1,6 +1,7 @@
 # The order of packages is significant, because pip processes them in the order
 # of appearance. Changing the order has an impact on the overall integration
 # process, which may cause wedges in the gate later.
+
 hacking<0.11,>=0.10.0
 pylint==1.7.6;python_version=='2.7' # GPLv2
 pylint;python_version>'3.0' #GPLv2
@@ -12,7 +13,8 @@ testrepository>=0.0.18 # Apache-2.0/BSD
 testtools>=2.2.0 # MIT
 
 # Doc requirements
-sphinx!=1.6.6,!=1.6.7,>=1.6.2 # BSD
+sphinx!=1.6.6,!=1.6.7,>=1.6.2,<2.0.0;python_version=='2.7'  # BSD
+sphinx!=1.6.6,!=1.6.7,>=1.6.2;python_version>='3.4'  # BSD
 openstackdocstheme>=1.18.1 # Apache-2.0
 
 # releasenotes