Adding error handler on upload stream

lib/storage-handler.js

@@ -114,6 +114,10 @@ exports.upload = function (provider, req, res, options, cb) {
     }
     var writer = provider.upload(uploadParams);
 
+    writer.on('error', function(err) {
+      self._error(err);
+    });
+
     var endFunc = function () {
       self._flushing--;
       var values = files[part.name];