refs #2615 return 409 on >1 background jobs

src/opengnsys/workers/oglive_worker.py

@@ -508,7 +508,7 @@ class ogLiveWorker(ServerWorker):
                 break
         if any_job_running:
             logger.info ('some job is already running, refusing to launch another one')
-            return { 'job_id': None, 'message': 'some job is already running, refusing to launch another one' }
+            raise Exception ({ '_httpcode': 409, '_msg': 'some job is already running, refusing to launch another one' })
 
         job_id = '{}-{}'.format (name, ''.join (random.choice ('0123456789abcdef') for _ in range (8)))
         import queue