Use Sphinx 1.5 warning-is-error

With pbr 2.0 and Sphinx 1.5, the setting for treat sphinx warnings as
errors is setting warning-is-error in build_sphinx section. Migrate the
setting from the old warnerrors one.

There are two issues:

- The `*` character is recognized as an emphasis character and must be
  escaped
- The index references modules that have since been removed

These are resolved.

Change-Id: Id078022c0f75bf8f162b693d260f67116eb6428b

doc/source/index.rst

@@ -24,8 +24,6 @@ API Documentation
    api/excutils
    api/fileutils
    api/fixture
-   api/fnmatch
-   api/imageutils
    api/importutils
    api/netutils
    api/reflection

oslo_utils/strutils.py

@@ -323,16 +323,16 @@ def mask_dict_password(dictionary, secret="***"):  # nosec
     A dictionary (which may contain nested dictionaries) contains
     information (such as passwords) which should not be revealed, and
     this function helps detect and replace those with the 'secret'
-    provided (or '***' if none is provided).
+    provided (or `***` if none is provided).
 
     Substitution is performed in one of three situations:
 
     If the key is something that is considered to be indicative of a
     secret, then the corresponding value is replaced with the secret
-    provided (or '***' if none is provided).
+    provided (or `***` if none is provided).
 
     If a value in the dictionary is a string, then it is masked
-    using the mask_password() function.
+    using the ``mask_password()`` function.
 
     Finally, if a value is a dictionary, this function will
     recursively mask that dictionary as well.

setup.cfg

@@ -22,13 +22,11 @@ classifier =
 packages =
     oslo_utils
 
-[pbr]
-warnerrors = true
-
 [build_sphinx]
+all-files = 1
+warning-is-error = 1
 source-dir = doc/source
 build-dir = doc/build
-all_files = 1
 
 [upload_sphinx]
 upload-dir = doc/build/html