Fix 'Module index' broken HTTP link

'Module Index' link points to HTML doc generated from source/api
RST files. These RST files are generated by pbr, by setting the
parameter 'autodoc_index_modules' to True.

Partial-Bug: #1535244
Change-Id: Ifceb5a140599d3968ea3d353b12c0bbe99d955e6

setup.cfg

@@ -62,6 +62,16 @@ watcher_workflow_engines =
 watcher_planners =
     default  = watcher.decision_engine.planner.default:DefaultPlanner
 
+[pbr]
+autodoc_index_modules = True
+autodoc_exclude_modules =
+    watcher.db.sqlalchemy.alembic.env
+    watcher.db.sqlalchemy.alembic.versions.*
+    watcher.tests.*
+    watcher_tempest_plugin.*
+    watcher.doc
+
+
 [build_sphinx]
 source-dir = doc/source
 build-dir = doc/build