Add callback for retry exhaustion

[dbowring]

E.g.,

@dramatiq.actor
def on_abandon_flaky_work(message_data, retry_info):
    logger.info("Too flaky, will not retry", message_data=message_data, retry_info=retry_info)

@dramatiq.actor(max_retries=5, on_retry_exhausted=on_abandon_flaky_work.actor_name)
def my_flaky_actor(*args, **kwargs):
    do_flaky_work(*args, **kwargs)

[dbowring]

@Bogdanp Is there any chance of this (or something like this) being merged?

[Bogdanp]

Sorry for the delay, this slipped under my radar. Thanks!