Running github-backup in a fresh clone of a repo for the first time, all the top-level API requests fail. It doesn't say why in that case, but I think this is a similar case that sheds light on it:

joey@darkstar:/tmp> github-backup joeyh
github-backup: Failed to query github for repos:
(StatusCodeException (Response {responseStatus = Status {statusCode = 403, statusMessage = "rate limit exceeded"}

Setting GITHUB_OAUTH_TOKEN before running it probably avoids the problem, but I've not tried it.

This is apparently the API rate limit blocking the first request. It used to be that a few hundred or thousand requests were allowed. I don't know if this has changed intentionally or what. --?Joey