Copy/Rename a page with a long reference should display a warning when the resulted path would be longer than 768 characters

STEPS TO REPRODUCE

1. Create a page with a reference shorter than 255 characters (e.g. 240 chars): ttttttttttttttttttttttttttttttt1/ttttttttttttttttttttttttttttttt2/ttttttttttttttttttttttttttttttt3/ttttttttttttttttttttttttttttttt4/ttttttttttttttttttttttttttttttt5/ttttttttttttttttttttttttttttttt6/ttttttttttttttttttttttttttttttt7/ttttttttttttttt8
2. Go to the top page from the hierarchy created
3. Click 'More Actions' > 'Copy' or 'Move / Rename'
4. Set another page with a longer name as copy location (e.g. Sandbox), make sure 'Preserve Children' is checked
5. Click 'Copy' or 'Rename' respectively

EXPECTED RESULTS

A warning is displayed (like the one from XWIKI-16415) on the fact that the path resulted is too long.

ACTUAL RESULTS

No warning is displayed. The operation displays 'Done', even if it failed (this is another issue described in XWIKI-17006) and the pages are partially copied/ moved.