4.2: url_keys: when deleting a page with an url_key, the url_key is not released in the Jahia system: the name could not be used later on even if no refererence is currently pointing to this url.

I Added some ulr_key on some of my pages. Then I deleted (and validated) one of the page with an url_key. I then tried to reuse the same url_key's name elsewhere on the site, but the engine prevents me of doing it. We should correctly release url_key when validating a page marked for deletion. If I remember correctly such a bug was already corrected on the 5.0.