Use deferred logging to report Class-Path manifest attribute problems

Closes gh-16883

Author: wilkinsona

spring-boot-project/spring-boot-devtools/src/main/java/org/springframework/boot/devtools/restart/ChangeableUrls.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2018 the original author or authors.
+ * Copyright 2012-2019 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.
@@ -178,7 +178,7 @@ private static List<URL> getUrlsFromManifestClassPathAttribute(URL jarUrl,
 			}
 		}
 		if (!nonExistentEntries.isEmpty()) {
-			System.out.println("The Class-Path manifest attribute in " + jarFile.getName()
+			logger.info("The Class-Path manifest attribute in " + jarFile.getName()
 					+ " referenced one or more files that do not exist: "
 					+ StringUtils.collectionToCommaDelimitedString(nonExistentEntries));
 		}