def locate_zephyr_base(checkout, version):
    """Locate the path to the Zephyr RTOS in a ChromiumOS checkout.

    Args:
        checkout: The path to the ChromiumOS checkout.
        version: The requested zephyr version, as a tuple of integers.

    Returns:
        The path to the Zephyr source.
    """
    return (checkout / 'src' / 'third_party' / 'zephyr' / 'main' /
            'v{}.{}'.format(*version[:2]))