Enable warning-is-error in doc build

- Fix docstring warnings
- pbr warnerrors is no longer needed.

Change-Id: I70532d99f34023b5fcce4373b6456cae2fbb642a

oslo_vmware/objects/datastore.py

@@ -195,6 +195,7 @@ class DatastorePath(object):
     file path to a virtual disk.
 
     Note:
+
     - Datastore path representations always uses forward slash as separator
       (hence the use of the posixpath module).
     - Datastore names are enclosed in square brackets.

setup.cfg

@@ -26,6 +26,7 @@ packages =
 source-dir = doc/source
 build-dir = doc/build
 all_files = 1
+warning-is-error = 1
 
 [upload_sphinx]
 upload-dir = doc/build/html
@@ -46,7 +47,6 @@ output_file = oslo_vmware/locale/oslo_vmware.pot
 
 [pbr]
 autodoc_index_modules = 1
-warnerrors = True
 autodoc_exclude_modules =
     oslo_vmware._i18n
     oslo_vmware.tests.*