Create a new Kaleo definition file based on the single-approver-workflow-definition.xml file and call it foo-workflow-definition.xml and edit the inside the markup of the file.
Go to the Control Panel
Under Portal, click "Workflow"
Click on the "Add" button
Don't give it a title
Upload the XML file
Back on the list of definitions, click on the Actions menu, and click on Edit
Edit the foo-workflow-definition.xml file in by making it invalid, perhaps by changing the value of one of the messages, so that you have an ampersand & character inside it.
Try to upload the new version of the foo-workflow-definition.xml file
If the bug still exists, you will be directed to a page titled "Error"
If the bug is fixed, then you should see a nice error message like "Invalid file format"
To reproduce: