def flowStopped(reason):
    """
        The flow has stopped.  The given L{Failure} object indicates why.
        After a L{IFount} invokes this method, it must stop invoking all other
        methods on this L{IDrain}; similarly, this L{IDrain} must stop invoking
        all methods on its L{IFount}.

        @param reason: The reason why the flow has terminated.  This may
            contain any exception type, depending on the L{IFount} delivering
            data to this L{IDrain}.
        @type reason: L{Failure}
        """
