Switch to newer openstackdocstheme and reno versions

Switch to openstackdocstheme 2.2.1 and reno 3.1.0 versions. Using
these versions will allow especially:
* Linking from HTML to PDF document
* Allow parallel building of documents
* Fix some rendering problems

Update Sphinx version as well.

Disable openstackdocs_auto_name to use 'project' variable as name.

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: If3e8d8ac29a728aa41562b31976ebe9bfa5df66f

doc/requirements.txt

@@ -2,7 +2,7 @@
 # of appearance. Changing the order has an impact on the overall integration
 # process, which may cause wedges in the gate later.
 
-openstackdocstheme>=1.18.1 # Apache-2.0
-sphinx!=1.6.6,!=1.6.7,!=2.1.0,>=1.6.2 # BSD
-reno>=2.5.0 # Apache-2.0
+openstackdocstheme>=2.2.1 # Apache-2.0
+sphinx>=2.0.0,!=2.1.0 # BSD
+reno>=3.1.0 # Apache-2.0
 sphinxcontrib-apidoc>=0.2.0  # BSD

doc/source/conf.py

@@ -28,11 +28,10 @@
 copyright = u'2015-2016, Various Authors'
 
 # openstackdocstheme options
-repository_name = 'openstack/diskimage-builder'
-bug_project = 'diskimage-builder'
-bug_tag = ''
-html_last_updated_fmt = '%Y-%m-%d %H:%M'
-
+openstackdocs_repo_name = 'openstack/diskimage-builder'
+openstackdocs_bug_project = 'diskimage-builder'
+openstackdocs_auto_name = False
+openstackdocs_bug_tag = ''
 
 # The language for content autogenerated by Sphinx. Refer to documentation
 # for a list of supported languages.
@@ -65,7 +64,7 @@
 #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 = []

releasenotes/source/conf.py

@@ -20,10 +20,10 @@
 copyright = u'2016, Diskimage-builder contributors'
 
 # openstackdocstheme options
-repository_name = 'openstack/diskimage-builder'
-bug_project = 'diskimage-builder'
-bug_tag = ''
-html_last_updated_fmt = '%Y-%m-%d %H:%M'
+openstackdocs_repo_name = 'openstack/diskimage-builder'
+openstackdocs_bug_project = 'diskimage-builder'
+openstackdocs_auto_name = False
+openstackdocs_bug_tag = ''
 
 # Release notes do not need a version in the title, they span
 # multiple versions.
@@ -62,7 +62,7 @@
 #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 = []