Expired Github token leads to empty FilesChanged view

[nikolaik]

Describe the bug
There is no way for a user to know how to fix the issue of bad github credentials, like in the case when the refresh_token is bad or expired.

Digging in the logs, we find these:

{
  "error": "No access_token in response"
  "funcName": "refresh_token"
  "gh_error": ["bad_refresh_token"]
  "gh_error_description": ["The refresh token passed is incorrect or expired."]
  "logger.name": "shared.torngit.github"
}

Could we allow this information to bubble up to the user some how?

Environment (please complete the following information):

Running a self-hosted instance

To Reproduce
Steps to reproduce the behavior:

1. Navigate to a pull request and the Files Changed view
2. Notice there is no data in the view, only the message "No Files covered by tests were changed"
3. Also notice an error in Pulls graphql query HTTP request
4. Also notice the above log message

Expected behavior
When navigating to the files changed view or any view that requires a working github auth token, surface token issues.

[zsalzbank]

This is happening to me too. Also on a self-hosted instance. I tried uninstalling the app from my organization and re installing it, but it didn't seem to help.

[drazisil-codecov]

@rohan-at-sentry