sometimes blows up

[davearonson]

Certain PRs result in an error message that "The change you wanted was rejected. Maybe you tried to change something you didn't have access to." Ones that have been merged or closed always seem to do this. Some that are open also do; these seem to be ones where the username has changed, so we can't grab it by that name. It seems like saving it calls validation which makes sure it's there and open. We should tell the user exactly what went wrong, rather than swallowing the Github error.