Retry on Gateway timeout response

src/main/java/org/genesys2/client/oauth/GenesysClient.java

@@ -267,7 +267,7 @@ public class GenesysClient {
 						LOG.error(new String(postBody));
 						LOG.error("HTTP response code: {}", response.getCode());
 						LOG.error("Response: {}", responseBody);
-						if (responseBody.contains("Deadlock found when trying to get lock; try restarting transaction")
+						if (response.getCode() == 504 || responseBody.contains("Deadlock found when trying to get lock; try restarting transaction")
 								|| responseBody.contains("nested exception is org.hibernate.exception.LockAcquisitionException: could not execute statement")
 								|| responseBody.contains("nested exception is org.hibernate.exception.LockTimeoutException: could not execute statement")) {
 							throw new PleaseRetryException(responseBody);