The print service indicates that a - possibly transient - problem
may require external intervention before the print service can
continue. One example of an event that can
generate this message is when the printer runs out of paper.
Not all print services may be capable of delivering interesting
events, or even telling when a job is complete. This message indicates
the print job has no further information or communication
with the print service. This message should always be delivered
if a terminal event (completed/failed/canceled) is not delivered.
For example, if messages such as JOB_COMPLETE have NOT been received
before receiving this message, the only inference that should be drawn
is that the print service does not support delivering such an event.
The job is not necessarily printed yet, but the data has been transferred
successfully from the client to the print service. The client may
free data resources.