It's not needed any more with Go 1.13 as we have wrapping/unwrapping in base
packages. All errors.Wrap calls are replaced with fmt.Errorf, some strings are
improved along the way.
The script is passed as a hex string, but no one should care. The hash is a
hex-encoded LE value, but no one should care either. Hex might change to
base64, LE to BE, no one outside these functions should care about that.
