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

Update Sphinx version as well.

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: I612722e75975d6cfd5fc61037834b675117019e7

doc/requirements.txt

@@ -1,4 +1,3 @@
-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,!=2.1.0,>=1.6.2;python_version>='3.4'  # BSD
-openstackdocstheme>=1.20.0 # Apache-2.0
-reno>=2.5.0 # Apache-2.0
+sphinx>=2.0.0,!=2.1.0 # BSD
+openstackdocstheme>=2.2.1 # Apache-2.0
+reno>=3.1.0 # Apache-2.0

doc/source/conf.py

@@ -23,9 +23,9 @@ extensions = [
 ]
 
 # openstackdocstheme options
-repository_name = 'openstack/os-vif'
-bug_project = 'os-vif'
-bug_tag = ''
+openstackdocs_repo_name = 'openstack/os-vif'
+openstackdocs_bug_project = 'os-vif'
+openstackdocs_bug_tag = ''
 
 # The suffix of source filenames.
 source_suffix = '.rst'
@@ -44,7 +44,7 @@ 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 ----------------------------------------------
 

lower-constraints.txt

@@ -34,7 +34,7 @@ msgpack-python==0.4.0
 msgpack==0.5.6
 netaddr==0.7.18
 netifaces==0.10.6
-openstackdocstheme==1.20.0
+openstackdocstheme==2.2.1
 os-client-config==1.28.0
 oslo.concurrency==3.20.0
 oslo.config==5.1.0
@@ -69,14 +69,14 @@ python-mimeparse==1.6.0
 python-subunit==1.0.0
 pytz==2018.3
 PyYAML==3.12
-reno==2.5.0
+reno==3.1.0
 repoze.lru==0.7
 requests==2.14.2
 requestsexceptions==1.2.0
 rfc3986==1.1.0
 Routes==2.4.1
 snowballstemmer==1.2.1
-Sphinx==1.6.2
+Sphinx==2.0.0
 sphinxcontrib-websupport==1.0.1
 statsd==3.2.2
 stestr==1.0.0

releasenotes/source/conf.py

@@ -40,7 +40,7 @@ release = ''
 version = ''
 
 # The name of the Pygments (syntax highlighting) style to use.
-pygments_style = 'sphinx'
+pygments_style = 'native'
 
 
 # -- Options for HTML output ----------------------------------------------