Activate network interfaces.

    Args:
      interfaces: list of string, the output device names to enable.
      logger: logger object, used to write to SysLog and serial port.

def _Ifup(self, interfaces, logger):
    """Activate network interfaces.

    Args:
      interfaces: list of string, the output device names to enable.
      logger: logger object, used to write to SysLog and serial port.
    """
    ifup = ['/usr/sbin/wicked', 'ifup', '--timeout', '1']
    try:
      subprocess.check_call(ifup + interfaces)
    except subprocess.CalledProcessError:
      logger.warning('Could not activate interfaces %s.', interfaces)