Enable the list of network interfaces.

    Args:
      interfaces: list of string, the output device names to enable.
      logger: logger object, used to write to SysLog and serial port.
      dhclient_script: string, the path to a dhclient script used by dhclient.

def EnableNetworkInterfaces(
      self, interfaces, logger, dhclient_script=None):
    """Enable the list of network interfaces.

    Args:
      interfaces: list of string, the output device names to enable.
      logger: logger object, used to write to SysLog and serial port.
      dhclient_script: string, the path to a dhclient script used by dhclient.
    """
    interfaces_to_up = [i for i in interfaces if i != 'eth0']
    if interfaces_to_up:
      logger.info('Enabling the Ethernet interfaces %s.', interfaces_to_up)
      self._WriteIfcfg(interfaces_to_up, logger)
      self._Ifup(interfaces_to_up, logger)