Use `Box<dyn Error>` as your error type, and you won't need to know about any other error type. They all convert automatically and propagate through the `?` ope

Use `Box<dyn Error>` as your error type, and you won't need to know about any other error type. They all convert automatically and propagate through the `?` operator. failure and anyhow crates are `Box<dyn Error>` on steroids.