message: use byte literal syntax.
diff: //! [2]: https://docs.rs/hex-buffer-serde/0.3.0/hex_buffer_serde/trait.Hex.html
  use alloc::{borrow::Cow, string::String, vec::Vec};
  use base16;
  -use core::{convert::TryFrom, fmt, marker::PhantomData};
  -use std::ops::RangeInclusive;
  +use core::{convert::TryFrom, fmt, marker::PhantomData, ops::RangeInclusive};
  use blake2::{Blake2b, Digest};
  use serde::{
  @@ -83,8 +82,8 @@ pub fn encode_iter(input: &(impl AsRef<[u8]> + ?Sized)) -> impl Iterator<Item =
  /// Returns true if all chars in a string are uppercase or lowercase.
  /// Returns false if the string is mixed case or if there are no alphabetic chars.
  fn string_is_same_case<T: AsRef<[u8]> + ?Sized>(s: &T) -> bool {
  - const LOWER_RANGE: RangeInclusive<u8> = 'a' as u8..='f' as u8;
  - const UPPER_RANGE: RangeInclusive<u8> = 'A' as u8..='F' as u8;
  + const LOWER_RANGE: RangeInclusive<u8> = b'a'..=b'f';
  + const UPPER_RANGE: RangeInclusive<u8> = b'A'..=b'F';
  let mut chars = s
  .as_ref()
  