Merge branch '1.8_release_4.0.x' into 1.10_release_4.0.x

Author: gituser

flinkx-ftp/flinkx-ftp-reader/src/main/java/com/dtstack/flinkx/ftp/reader/FtpSeqBufferedReader.java

@@ -77,7 +77,7 @@ private void nextStream() throws IOException{
             String file = iter.next();
             InputStream in = ftpHandler.getInputStream(file);
             if (in == null) {
-                throw new NullPointerException();
+                throw new RuntimeException(String.format("can not get inputStream for file [%s], please check file read and write permissions", file));
             }
 
             br = new BufferedReader(new InputStreamReader(in, charsetName));