1. Create an assignment with the grading method set to 'Rubric'.
2. Click on the assignment and select 'Advanced grading' from the menu.
3. Click on 'Define new grading form from scratch'.
4. Save the rubric.
5. Click on 'Publish the form as a new template'.
6. Click on 'Continue' at the confirmation screen.
7. Notice you get the message 'The form was successfully saved as a templateclick to close' at the top.

This also happens with the grading method is set to 'Marking guide' but I suspect there is only one place this needs to be addressed in the code.