turn on warning-is-error in sphinx build

Fix a formatting error in one docstring and turn on the flag to ensure
that future warnings in the doc build trigger a build failure.

Change-Id: I7159b985d1690a8ae61ff885408da4623c105952
Signed-off-by: Doug Hellmann <doug@doughellmann.com>

doc/source/index.rst

@@ -3,7 +3,7 @@
 ==============================================
 
 This is a client for the OpenStack Images API. There's :doc:`a Python
-API <library/api/index>` (the :mod:`glanceclient` module) and a
+API <reference/api/index>` (the :mod:`glanceclient` module) and a
 :doc:`command-line script <cli/glance>` (installed as
 :program:`glance`).
 

glanceclient/common/utils.py

@@ -311,7 +311,7 @@ def get_file_size(file_obj):
     """Analyze file-like object and attempt to determine its size.
 
     :param file_obj: file-like object.
-    :retval The file's size or None if it cannot be determined.
+    :retval: The file's size or None if it cannot be determined.
     """
     if (hasattr(file_obj, 'seek') and hasattr(file_obj, 'tell') and
             (six.PY2 or six.PY3 and file_obj.seekable())):

setup.cfg

@@ -36,6 +36,7 @@ console_scripts =
 [build_sphinx]
 builders = html,man
 all-files = 1
+warning-is-error = 1
 source-dir = doc/source
 build-dir = doc/build