Function scheme_disabled 

fn scheme_disabled(scheme: &'static str) -> ApiError

SchemeDisabled: the scheme is one this server recognises, and this route does not accept it. The message names the routes that do.

Its own name and its own status (403, not 401) so a client can tell this apart from authentication_required by the name alone: retrying with a different credential of the same kind will not help either, because the kind itself is off here.