message: ErrorCode adjustments
diff: -use core::{convert::TryFrom, fmt, mem::transmute};
  +use core::{convert::TryFrom, mem::transmute};
  // TODO: Add a ufmt debug implementation for process binaries to use.
  -/// A [TRD 104 error code][error-codes] returned by the kernel.
  +/// An error code the Tock kernel may return, as specified in
  +/// [TRD 104][error-codes]. Note that `BADRVAL` is not included, as it cannot be
  +/// produced by the Tock kernel.
  ///
  /// [error-codes]: https://github.com/tock/tock/blob/master/doc/reference/trd104-syscalls.md#33-error-codes
  #[derive(Clone, Copy, Debug, PartialEq, Eq)]
  @@ -232,15 +234,9 @@ pub enum ErrorCode {
  }
  /// The provided value is not a recognized TRD 104 error code.
  -#[derive(PartialEq, Eq)]
  +#[derive(PartialEq, Eq, Debug)]
  pub struct NotAnErrorCode;
  -impl fmt::Debug for NotAnErrorCode {
  - fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  - f.write_str("not an error code")
  - }
  -}
  -
  impl TryFrom<u32> for ErrorCode {
  type Error = NotAnErrorCode;
  