fixes transaction deadlocks causing exceptions

jobs.py

@@ -141,8 +141,10 @@ def jobs_schedule(hostname):
 	if not hostdata:
 		return 'no hostdata sent', 400
 	job = None
+	tries = 0
 	jobtypes = hostdata['jobtypes'] if 'jobtypes' in hostdata else []
 	while (not job):
+		try:
 			query("BEGIN")
 			for i in query('SELECT * FROM jobs WHERE state = "ready" ORDER BY priority DESC'):
 				if i['type'] in hostdata['jobtypes'] and \
@@ -152,9 +154,12 @@ def jobs_schedule(hostname):
 			if not job:
 				return 'no jobs', 503
 			modify('UPDATE jobs SET state="scheduled", worker = ?, time_scheduled = ? WHERE id = ?', hostname, datetime.now(), job['id']) 
-		try:
 			query("COMMIT")
-		except:
+		except OperationalError:
+			tries += 1
 			job = None
 			sleep(random.randinti(0,50))
+			if tries > 10:
+				return 'no jobs', 503
+
 	return Response(json.dumps(job, default=date_json_handler), mimetype='application/json')