bin/update fails if a repo is deleted or renamed

[krisleech]

It looks like unsymbol/ribimaybe has changed ownership to filib/ribimaybe.

The API, unlike the web UI, does not redirect to the new owner and returns a 404 which raises an exception. This sounds like a bug with the Github API.

Not sure if we want to catch 404's or let them blow up (so the repo can be fixed). Happy to submit a PR.

[solnic]

Ooops :) Looks like some audit script would be nice that would verify things so we can update the db properly.