Before this commit, UTM was no more set for website.page. Website.page mechanism uses the _handle_exception to check if an url match a record in database, instead of use the method _dispatch that uses controllers. Consequently, module UTM never set the utm into the cookies for website.page. Now we override method '_handle_exception' that will anyway ignore to set utm if it is a real exception and not a fallback (redirect, page, attachment, ...)