message: nicer diff formating
diff: @@ -39,8 +39,8 @@ script:
  cat stdout.real stderr.real &&
  # Test `cargo miri` output. Not on mac because output redirecting doesn't
  # work. There is no error. It just stops CI.
  - diff stdout.ref stdout.real &&
  - diff stderr.ref stderr.real
  + diff -u stdout.ref stdout.real &&
  + diff -u stderr.ref stderr.real
  fi &&
  # Test `cargo miri test`
  #cargo miri test &&
  