Bump openstackdocstheme to 1.20.0

Some options are now automatically configured by the version 1.20:
- project
- html_last_updated_fmt
- latex_engine
- latex_elements
- version
- release.

Change-Id: Iad7ed84d2560c7829be20c24e41299b60283cccb
diff --git a/doc/requirements.txt b/doc/requirements.txt
index 67530ff..b03ff2c 100644
--- a/doc/requirements.txt
+++ b/doc/requirements.txt
@@ -1,7 +1,8 @@
 # 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.
-sphinx!=1.6.6,!=1.6.7,>=1.6.2 # BSD
-openstackdocstheme>=1.18.1 # Apache-2.0
+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
 sphinxcontrib-apidoc>=0.2.0  # BSD
diff --git a/doc/source/conf.py b/doc/source/conf.py
index 45d8021..57d763e 100755
--- a/doc/source/conf.py
+++ b/doc/source/conf.py
@@ -63,7 +63,7 @@
 master_doc = 'index'
 
 # General information about the project.
-project = u'patrole'
+
 copyright = u'2017, Patrole Developers'
 
 # If true, '()' will be appended to :func: etc. cross-reference text.
@@ -93,15 +93,15 @@
 html_last_updated_fmt = '%Y-%m-%d %H:%M'
 
 # Output file base name for HTML help builder.
-htmlhelp_basename = '%sdoc' % project
+htmlhelp_basename = 'patroledoc'
 
 # Grouping the document tree into LaTeX files. List of tuples
 # (source start file, target name, title, author, documentclass
 # [howto/manual]).
 latex_documents = [
     ('index',
-     '%s.tex' % project,
-     u'%s Documentation' % project,
+     'patrole.tex',
+     u'patrole Documentation',
      u'Patrole Developers', 'manual'),
 ]