Provides a simple trait that unwraps the locks provide by [std::sync::RwLock].
In every case, this is the same as calling .expect("lock poisoned"). However, it
does not use .unwrap() or .expect(), which makes it easier to distinguish from
other forms of unwrapping when reading code.
use OrPoisoned;
use RwLock;
let lock = new;
let read = lock.read.or_poisoned;
// this is identical to
let read = lock.read.unwrap;