def process_returned_message(basic_return, metadata, payload)
      response_queue = @transactions.delete metadata[:message_id]
      response_queue << MessageNotDeliveredError if response_queue
    end
def process_returned_message(basic_return, metadata, payload)
      response_queue = @transactions.delete metadata[:message_id]
      response_queue << MessageNotDeliveredError if response_queue
    end
process a returned message

 If a message is sent to a queue that cannot be found,
 rabbitmq returns that message to this method