Rust `Error` `description` deprecated

[CosmicHorrorDev]

Implementing .description() for Error was deprecated in rust 1.42 (link) where instead it is recommended to impl Display or .to_string().

Since it was deprecated it would be good to switch CuckooError away from using .description(), and it already implements Display: however, the text for Display and .description() are different. I would recommend using the text from .description() for Display since the text in Display is already just the Debug text, but I wanted to get your all's input.