pub fn spawn_async_with_pipes<P: AsRef<Path>, T: FromRawFd, U: FromRawFd, V: FromRawFd>(
    working_directory: P,
    argv: &[&Path],
    envp: &[&Path],
    flags: SpawnFlags,
    child_setup: Option<Box_<dyn FnOnce() + 'static>>
) -> Result<(Pid, T, U, V), Error>