Clean retry in deferred.defer
If you raise a deferred.SingularTaskFailure it will set an error HTTP-status, but there won't be an exception in the log.
I am using deferred.defer quite heavily to schedule tasks using push queues on AppEngine. 
Sometimes I wish I would have a clean way to signal a retry for a task without having to raise an Exception that generates a log warning.
Is there a way to do this?