def assignment_reassigned(self, participant):
self.fail_participant(participant)<EOL>
What to do if the assignment assigned to a participant is
        reassigned to another participant while the first participant
        is still working.

        This runs when a participant is created with the same assignment_id
        as another participant if the earlier participant still has the status
        "working". Calls :func:`~dallinger.experiments.Experiment.fail_participant`.