Log rejected listener container tasks at warn level

Closes gh-27451

spring-jms/src/main/java/org/springframework/jms/listener/AbstractJmsListeningContainer.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2020 the original author or authors.
+ * Copyright 2002-2021 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -582,13 +582,13 @@ public abstract class AbstractJmsListeningContainer extends JmsDestinationAccess
 	/**
 	 * Log a task that has been rejected by {@link #doRescheduleTask}.
 	 * <p>The default implementation simply logs a corresponding message
-	 * at debug level.
+	 * at warn level.
 	 * @param task the rejected task object
 	 * @param ex the exception thrown from {@link #doRescheduleTask}
 	 */
 	protected void logRejectedTask(Object task, RuntimeException ex) {
-		if (logger.isDebugEnabled()) {
+		if (logger.isWarnEnabled()) {
-			logger.debug("Listener container task [" + task + "] has been rejected and paused: " + ex);
+			logger.warn("Listener container task [" + task + "] has been rejected and paused: " + ex);
 		}
 	}