Also ensure errors in this.writer.close that are not sent to the ca…

…llback are captured subsequently and included in the callback.

lib/writer.js

@@ -265,15 +265,15 @@ class ParquetTransformer extends stream.Transform {
   _transform(row, encoding, callback) {
     if (row) {
       this.writer.appendRow(row)
-        .then(callback)
-        .catch(e => callback(e));
+        .then(d => callback(null,d), callback);
     } else {
       callback();
     }
   }
 
   _flush(callback) {
-    this.writer.close(callback);
+    this.writer.close(callback)
+      .then(d => callback(null, d), callback);
   }
 
 }