The publish button ends up being disabled while the changes made to the

model are being saved, so that the user does not repeatedly click the

publish button. If the request fails due to an error with one of the

fields that were changed, then the publish button does not ever end up

being re-enabled. Now, the model emits an event when an error happens

in the above case, and the view listens for that event being published.

When the view is notified of that event, it re-enables the buttons.

I tested this locally by following the instructions listed on the bug
report page (bug #4777).

I also ran the JavaScript unit tests.