Merge branch 'master' into module-support

docs/patterns/index.rst

@@ -10,6 +10,9 @@ changes are they will open a database connection at the beginning of the
 request and get the information of the currently logged in user.  At the
 end of the request, the database connection is closed again.
 
+There are more user contributed snippets and patterns in the `Flask
+Snippet Archives <http://flask.pocoo.org/snippets/>`_.
+
 .. toctree::
    :maxdepth: 2
 

flask.py

@@ -931,10 +931,7 @@ class Flask(_PackageBoundObject):
         :param rv: the return value from the view function
         """
         if rv is None:
-            from warnings import warn
-            warn(Warning('View function did not return a response'),
-                 stacklevel=2)
-            return u''
+            raise ValueError('View function did not return a response')
         if isinstance(rv, self.response_class):
             return rv
         if isinstance(rv, basestring):