Error is thrown when not connected to internet (or GitHub is down)

[mitchhentges]

I had a brief amount of server downtime recently (I know, the shame), and sentry-auth-github threw the error: 'ConnectionError' object has no attribute 'status_code'.

Sounds like when the request to GitHub fails, due to a network issue, the returned object doesn't have a status code (which makes sense considering the server couldn't be contacted).

In sentry-auth-github, we need to handle the situation where the request to GitHub fails