GitHub auth issue with read-only users

[foresmac]

I'll describe the problems we ran into this morning on a project; not sure about the best way to resolve them.

A read-only user was added to a private repo, which prevented the webhook from updating the GitHub status about the coverage. Here is the error message:

Unable to set pending status to vokal/project-api/54825ba as username, user's oauth token may have expired, not have push access for the repo, or the sha may not exist: {"message":"Not Found","documentation_url":"https://developer.github.com/v3"}

That read-only user was then removed from the repo, but since I believe the user's auth token was cached, CVR could no longer access new commits to properly add updated coverage reports:

The commit 54825ba does not exist

But we verified that was the correct commit.

[jrit]

Note this appears to have happened for a user that had push rights which were revoked. That doesn't make the issue less valid, cvr should be able to recover better on those types of permission failures.