2 Checks for usage of `option_env!(...).unwrap()` and
3 suggests usage of the `env!` macro.
6 Unwrapping the result of `option_env!` will panic
7 at run-time if the environment variable doesn't exist, whereas `env!`
8 catches it at compile-time.
12 let _ = option_env!("HOME").unwrap();
15 Is better expressed as: