add warning message for empty redis queue

import json

import time

import warnings

import numpy as np

    msg : dict

          The message from the processing queue.

    """

    # Check if the redis queue is empty

    msg = queue.rpop(inqueue)

    if msg is None:

        warnings.warn('Expected to process a cluster job, but the message queue is empty.')

        sys.exit()

    # Load the message out of the processing queue and add a max processing time key

    msg = json.loads(queue.rpop(inqueue), object_hook=object_hook)

    msg = json.loads(msg, object_hook=object_hook)

    msg['max_time'] = time.time() + slurm_walltime_to_seconds(msg['walltime'])

    # Push the message to the processing queue with the updated max_time