Switch to newer openstackdocstheme version

Switch to openstackdocstheme 2.2.1 version. Using
this version will allow especially:
* Linking from HTML to PDF document
* Allow parallel building of documents
* Fix some rendering problems

Update Sphinx version as well.

Set openstackdocs_pdf_link to link to PDF file. Note that
the link to the published document only works on docs.openstack.org
where the PDF file is placed in the top-level html directory. The
site-preview places the PDF in a pdf directory.

Set openstackdocs_auto_version to not auto-version the documents.

Set openstackdocs_auto_name to use 'project' as name.

openstackdocstheme renames some variables, so follow the renames
before the next release removes them. A couple of variables are also
not needed anymore, remove them.

Change pygments_style to 'native' since old theme version always used
'native' and the theme now respects the setting and using 'sphinx' can
lead to some strange rendering.

See also
http://lists.openstack.org/pipermail/openstack-discuss/2020-May/014971.html

Change-Id: I26887b175b9c1ced7347289b7d5d4f57a20ec36a

Author: ajaeger

doc/requirements.txt

@@ -2,8 +2,8 @@ pbr>=2.0.0,!=2.1.0
 
 Pygments
 docutils
-sphinx>=2.0.0,!=2.1.0
-openstackdocstheme>=2.0.0
+sphinx>=2.0.0,!=2.1.0 # BSD
+openstackdocstheme>=2.2.1 # Apache-2.0
 nwdiag
 blockdiag
 sphinxcontrib-blockdiag

doc/source/conf.py

@@ -30,9 +30,15 @@
                'sphinxcontrib.nwdiag' ]
 
 # openstackdocstheme options
-repository_name = 'openstack-dev/devstack'
-bug_project = 'devstack'
-bug_tag = ''
+openstackdocs_repo_name = 'openstack-dev/devstack'
+openstackdocs_pdf_link = True
+openstackdocs_bug_project = 'devstack'
+openstackdocs_bug_tag = ''
+openstackdocs_auto_name = False
+# This repo is not tagged, so don't set versions
+openstackdocs_auto_version = False
+version = ''
+release = ''
 
 todo_include_todos = True
 
@@ -81,7 +87,7 @@
 show_authors = False
 
 # The name of the Pygments (syntax highlighting) style to use.
-pygments_style = 'sphinx'
+pygments_style = 'native'
 
 # A list of ignored prefixes for module index sorting.
 modindex_common_prefix = ['DevStack-doc.']