That informs you that updater failed updates check because it could not resolve repo.turris.cz. This is most probably because at time of its execution router was without internet connection.
Please check time sequence. Most probably your router ran updater just in time when we were deploying new version. That causes miss match between downloaded files and their signatures (either one of them can be from new release instead of older one). That results to signature validation failure. In such case updater does no change to system. Subsequent update should be from later time and is another updater execution (this time with new system update).