What a client sent for a page is not valid (Pages::saveDraft): a 422, with what is wrong field by field in $errors -- slug, sections/2/data/title... -- for the page editor to show next to each one.
class MMO\editor\exceptions\eInvalidPage extends MMO\core\exceptions\eInvalid
Collect every listener for this class, including those registered on its parent classes (so a subclass event is also caught by listeners of its parent event), sorted by ascending $order (ties keep …
Change the order of an already-registered listener, whether added directly via AddListener or indirectly via ConnectListeners (which also stores its [$obj, $methodName] callables here).