Replace deprecated osloshpinx with openstackdocstheme

This change fixes the broken tox docs target by following a change
fixing the same problem in the tripleo-specs repo:
  https://review.opendev.org/651440

We have to bump sphinx and yasfb versions. For the new sphinx we have
to switch to python3 in all tox envs.

Also change zuul config to run py3 jobs instead of py2.

If testr happens to complain about 'db type could not be determined'
please delete the .testrepository folder. The problem should not come
back or appear in the gate at all. For an explanation please see
bug #1229445.

Change-Id: I57d5bd318732bf9d6b685f95ba473d51bffa1f67
Related-Bug: #1229445
Related-Change: https://review.opendev.org/651440
Story: #2005536
Task: #30674

.zuul.yaml

@@ -3,7 +3,7 @@
       - openstack-specs-jobs
     check:
       jobs:
-        - openstack-tox-py27
+        - openstack-tox-py36
     gate:
       jobs:
-        - openstack-tox-py27
+        - openstack-tox-py36

doc/source/conf.py

@@ -24,7 +24,7 @@ sys.path.insert(0, os.path.abspath('../..'))
 extensions = [
     'sphinx.ext.autodoc',
     #'sphinx.ext.intersphinx',
-    'oslosphinx',
+    'openstackdocstheme',
     'yasfb',
 ]
 
@@ -76,6 +76,8 @@ pygments_style = 'sphinx'
 # html_theme = '_theme'
 # html_static_path = ['static']
 
+html_theme = 'openstackdocs'
+
 # Output file base name for HTML help builder.
 htmlhelp_basename = '%sdoc' % project
 

requirements.txt

@@ -1,4 +1,3 @@
-pbr>=0.6,<1.0
-oslosphinx
-sphinx>=1.1.2,<1.2
-yasfb>=0.5.1
+openstackdocstheme
+sphinx>=2.0.0
+yasfb>=0.8.0

tox.ini

@@ -1,9 +1,10 @@
 [tox]
 minversion = 1.6
-envlist = docs,py27
+envlist = docs,py36
 skipsdist = True
 
 [testenv]
+basepython = python3
 usedevelop = True
 install_command = pip install -U {opts} {packages}
 setenv =