Let event be the result of using .
Set event’s
[type](https://www.w3.org/TR/dom41/#dom-event-type)
attribute to “error
“.Let legacyOutputDidListenersThrowFlag be initially unset.
Dispatch event at with legacyOutputDidListenersThrowFlag.
If the event’s canceled flag is not set, run the steps to using transaction and request‘s .