function updatePriceFromRealUnicornPrice() {
    require(block.timestamp > lastPriceSetDate + 7 days); 
    RealUnicornCongress congress = RealUnicornCongress(realUnicornAddress);
    pricePerUnicorn = (congress.priceOfAUnicornInFinney() * 1 finney) / 1000;
    PriceUpdate(pricePerUnicorn, msg.sender);
  }