def _run_apt_command(cmd, fatal=False):
    """Run an apt command with optional retries.

    :param: cmd: str: The apt command to run.
    :param: fatal: bool: Whether the command's output should be checked and
        retried.
    """
    # Provide DEBIAN_FRONTEND=noninteractive if not present in the environment.
    cmd_env = {
        'DEBIAN_FRONTEND': os.environ.get('DEBIAN_FRONTEND', 'noninteractive')}

    if fatal:
        _run_with_retries(
            cmd, cmd_env=cmd_env, retry_exitcodes=(1, APT_NO_LOCK,),
            retry_message="Couldn't acquire DPKG lock")
    else:
        env = os.environ.copy()
        env.update(cmd_env)
        subprocess.call(cmd, env=env)
Run an apt command with optional retries.

    :param: cmd: str: The apt command to run.
    :param: fatal: bool: Whether the command's output should be checked and
        retried.