------------------------------------------------------------------------------
changeState :: (HeistState (Handler a a) -> HeistState (Handler a a))
            -> Heist a
            -> Heist a
changeState _ (Configuring _)  =
    error "changeState: HeistState has not been initialized"
changeState :: (HeistState (Handler a a) -> HeistState (Handler a a))
            -> Heist a
            -> Heist a
changeState _ (Configuring _)  =
    error "changeState: HeistState has not been initialized"
changeState _ (Configuring _)  =
    error "changeState: HeistState has not been initialized"