# File lib/ruote/engine.rb, line 419
    def unregister_participant (name_or_participant)

      re = @context.plist.unregister(name_or_participant)

      raise(ArgumentError.new('participant not found')) unless re

      @context.storage.put_msg(
        'participant_unregistered',
        'regex' => re.to_s)
    end