writeln!(
        std::io::stderr(),
        "Error while running {:?}: {}",
        cmd,
        std::process::Command::new(&cmd).args(args).exec()
    )
    .unwrap_or(());
    std::process::exit(1)

    let err = std::process::Command::new(&cmd).args(args).exec();
    report_external_command_error(&command[0], err);

            writeln!(std::io::stderr(), "Error while running {:?}: {}", cmd, e).unwrap_or(());
            std::process::exit(1)

            report_external_command_error(&command[0], e);

fn report_external_command_error(cmd: &OsString, err: std::io::Error) -> ! {
    if err.kind() == std::io::ErrorKind::NotFound {
        writeln!(std::io::stderr(), "No such subcommand: {:?}", cmd).unwrap_or(());
    } else {
        writeln!(std::io::stderr(), "Error while running {:?}: {}", cmd, err).unwrap_or(());
    }
    std::process::exit(1)
}