JobMessageSeverity can be one of:
(0) An informative message is generated during the job's execution, such as a job uploading data, job progressing on a server or job results. This message type never indicates a problem.
(1) A warning message is generated when a job experiences a situation that may cause a problem during its execution or when the result may not be what you expect. For example, when the job has failed to take a layer offline from an online map. Generally the job will run to successful completion even if there are one or more warnings.
(2) An error message indicates a critical event that caused the job to fail. The error instance is also available from the job's error property.
(-1) A message of unknown severity.