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.

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.

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.

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

Change-Id: I18c53d2d0fbf2929cafd0c995c72a0b20ad809e9

doc/source/conf.py

@@ -25,7 +25,7 @@ extensions = [
 ]
 
 # Feed configuration for yasfb
-feed_base_url = 'http://specs.openstack.org/openstack/tripleo-specs'
+feed_base_url = 'https://specs.openstack.org/openstack/tripleo-specs'
 feed_author = 'OpenStack TripleO Team'
 
 exclude_patterns = [
@@ -33,6 +33,11 @@ exclude_patterns = [
     '**/policy-template.rst',
 ]
 
+# openstackdocstheme options
+openstackdocs_repo_name = 'openstack/tripleo-specs'
+openstackdocs_bug_project = 'tripleo'
+openstackdocs_bug_tag = ''
+
 # autodoc generation is a bit aggressive and a nuisance when doing heavy
 # text edit cycles.
 # execute "export SPHINX_DEBUG=1" in your terminal to disable
@@ -55,7 +60,7 @@ add_function_parentheses = True
 add_module_names = True
 
 # The name of the Pygments (syntax highlighting) style to use.
-pygments_style = 'sphinx'
+pygments_style = 'native'
 
 # -- Options for HTML output --------------------------------------------------
 

requirements.txt

@@ -1,5 +1,5 @@
-openstackdocstheme>=1.32.1
-sphinx>=2.0.0
+openstackdocstheme>=2.2.1 # Apache-2.0
+sphinx>=2.0.0,!=2.1.0 # BSD
 stestr>=2.0.0 # Apache-2.0
 testtools>=0.9.34
 yasfb>=0.8.0