Why MonadError instance for ChronicleT uses underlying monad

[phadej]

Can it be made lawful directly. Why if not? Add to documentation

[mutantmell]

I believe that this is a valid instance:

instance (Semigroup c, Monad m) => MonadError c (ChronicleT c m) where
    throwError = confess
    catchError (ChronicleT m) handler = ChronicleT $ do
      a <- m
      case a of
        This  x   -> runChronicleT $ handler x
        That    y -> return $ That y
        These _ y -> return $ That y

It discards errors from a 'These' constructor, which is consistent with the idea that 'These' represents non-fatal error states.