use done event to signal write success (just like in extract)

src/backups.js

@@ -394,6 +394,12 @@ function createWriteStream(destFile, encryption) {
         ps.emit('error', new BoxError(BoxError.FS_ERROR, `Write error ${destFile}: ${error.message}`));
     });
 
+    stream.on('finish', function () {
+        debug('createWriteStream: done.');
+        // we use a separate event because ps is a through2 stream which emits 'finish' event indicating end of inStream and not write
+        ps.emit('done');
+    });
+
     if (encryption) {
         let decrypt = new DecryptStream(encryption);
         decrypt.on('error', function (error) {
@@ -749,7 +755,7 @@ function downloadDir(backupConfig, backupFilePath, dataLayout, progressCallback,
 
                     progressCallback({ message: `Downloading ${entry.fullPath} to ${destFilePath}` });
 
-                    sourceStream.pipe(destStream, { end: true }).on('finish', closeAndRetry);
+                    sourceStream.pipe(destStream, { end: true }).on('done', closeAndRetry);
                 });
             }, done);
         });