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**BACKWARD-INCOMPATIBLE CHANGES**
* Custom encoder/decoder support has been moved to a centralized
registry in ``carrot.serialization``. This means the
``encoder``/``decoder`` optional arguments to ``Publisher.send``
`(and the similar attributes of ``Publisher`` and ``Consumer``
classes) no longer exist. See ``README`` for details of the new
system.
* Any ``Consumer`` and ``Publisher`` instances should be
upgraded at the same time since carrot now uses the AMQP
``content-type`` field to know how to automatically de-serialize
your data. If you use an old-style ``Publisher`` with a new-style
``Consumer``, you will get a raw string back as ``message_data``
instead of your de-serialized data. An old-style ``Consumer``
will work with a new-style ``Publisher`` as long as you're using
the default ``JSON`` serialization methods.
* Acknowledging/Rejecting/Requeuing a message twice now raises
an exception.
*ENHANCEMENTS*
* ``ConsumerSet``: Receive messages from several consumers.