HDFS-10417. Improve error message from checkBlockLocalPathAccess. Contributed by Tianyin Xu.

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DataNode.java

@@ -1717,7 +1717,8 @@ private void checkBlockLocalPathAccess() throws IOException {
       throw new AccessControlException(
           "Can't continue with getBlockLocalPathInfo() "
               + "authorization. The user " + currentUser
-              + " is not allowed to call getBlockLocalPathInfo");
+              + " is not configured in "
+              + DFSConfigKeys.DFS_BLOCK_LOCAL_PATH_ACCESS_USER_KEY);
     }
   }