Partial merge of develop to experimental

Does not include #2336 as the file has been moved out from underneath it:
will do this separately

src/ContentMessages.js

@@ -377,9 +377,9 @@ class ContentMessages {
                 }
             }
             if (error) {
-                dis.dispatch({action: 'upload_failed', upload: upload});
+                dis.dispatch({action: 'upload_failed', upload, error});
             } else {
-                dis.dispatch({action: 'upload_finished', upload: upload});
+                dis.dispatch({action: 'upload_finished', upload});
             }
         });
     }