approve pull + logout == failure

[braddr]

Logging out tosses away the github access token. In the future, when conditions are met and an attempt to perform the merge happens, the check to make sure the user is still authorized to merge fails. If that step was omitted the merge itself would also fail.

Another failure mode that can occur is if the user is still logged in to the a-t, thus we still have an access token, but it's been revoked on github.

None of these errors are surfaced to the ui in any way.