Queue API callback_queue_worker() may throw exceptions to indicate the whole queue has a problem

The Queue API worker callback, callback_queue_worker may throw an exception of class Drupal\Core\Queue\SuspendQueueException to indicate to the queue runner that it has encountered a problem which will affect the whole queue. Examples of such conditions are network outage, a 3rd party service being unavailable, etc.

A queue runner should catch this exception, distinctly from an ordinary Exception, and skip processing of items from the worker's queue. It is up to the runner to determine when it is safe to try that queue again.