∀ {ε : Type u_1} {α : Type u_2} (motive : Except ε α → Sort u_3) (err : ε) (h_1 : (err : ε) → motive (Except.error err))
  (h_2 : (v : α) → motive (Except.ok v)),
  (match Except.error err with
    | Except.error err => h_1 err
    | Except.ok v => h_2 v) =
    h_1 err