Run the OS Login NSS cache binary.

    Returns:
      int, the return code from the call, or None if the script is not found.

def _RunOsLoginNssCache(self):
    """Run the OS Login NSS cache binary.

    Returns:
      int, the return code from the call, or None if the script is not found.
    """
    try:
      return subprocess.call([constants.OSLOGIN_NSS_CACHE_SCRIPT])
    except OSError as e:
      if e.errno == errno.ENOENT:
        return None
      else:
        raise