/// Use the `unwrap_fmt!` macro instead.
///
/// The only reason this exists is because `Option` and `Result`
/// have a different number of arguments for `unwrap_or_else` so
/// it's not possible to use the same macro for both.
///
/// If you for whatever reason want your custom type to be
/// unwrappable with this macro, then go ahead and implement
/// this trait, I guess.