Conduit responds to requests with either ERR-INVALID-SESSION or ERR-INVALID-AUTH if the request wasn't sufficiently authenticated. Arcanist's patch workflow can automatically attempt to recover from situations in which Conduit responds to unauthenticated requests with ERR-INVALID-SESSION (by resending an authenticated version of the request), but not ERR-INVALID-AUTH - recover from ERR-INVALID-AUTH in the same way.
Closes T15333