krakenExchange logs better error message when trading pair is missing

plugins/krakenExchange.go

@@ -196,8 +196,7 @@ func getFieldValue(object krakenapi.BalanceResponse, fieldName string) float64 {
 func (k *krakenExchange) GetOrderConstraints(pair *model.TradingPair) *model.OrderConstraints {
 	constraints, ok := krakenPrecisionMatrix[*pair]
 	if !ok {
-		log.Printf("krakenExchange could not find orderConstraints for trading pair %v, returning nil\n", pair)
-		return nil
+		panic(fmt.Sprintf("krakenExchange could not find orderConstraints for trading pair %v. Try using the \"ccxt-kraken\" integration instead.", pair))
 	}
 	return &constraints
 }