no error if network is down

oml/localnodes.py

@@ -186,6 +186,8 @@ class LocalNodes4(LocalNodesBase):
             s.setsockopt (socket.IPPROTO_IP, socket.IP_MULTICAST_TTL, self._TTL)
             try:
                 s.sendto(packet + b'\0', sockaddr)
+            except OSError:
+                pass
             except:
                 logger.debug('LocalNodes4.send failed', exc_info=True)
             s.close()