Run the ``list_queues`` command (for the default vhost) and return a
        list of tuples describing the queues.

        :return:
            A list of 2-element tuples. The first element is the queue name,
            the second is the current queue size.

def list_queues(self):
        """
        Run the ``list_queues`` command (for the default vhost) and return a
        list of tuples describing the queues.

        :return:
            A list of 2-element tuples. The first element is the queue name,
            the second is the current queue size.
        """
        lines = output_lines(
            self.exec_rabbitmqctl_list('queues', ['-p', self.vhost]))
        return [tuple(line.split(None, 1)) for line in lines]