https://travis-ci.org/github/bitcoin/bitcoin/jobs/679885530#L8791
nChangePosInOut = GetRandInt(txNew.vout.size()+1);
                        }
                        else if ((unsigned int)nChangePosInOut > txNew.vout.size())
                        {
                            error = _("Change index out of range");
                            return false;
                        }
                        std::vector<CTxOut>::iterator position = txNew.vout.begin()+nChangePosInOut;
                        txNew.vout.insert(position, newTxOut);
                    }
                } else {
                    nChangePosInOut = -1;
                }
                
                
                for (const auto& coin : setCoins) {
                    txNew.vin.push_back(CTxIn(coin.outpoint,CScript()));
                }
                tx_sizes = CalculateMaximumSignedTxSize(CTransaction(txNew), this, coin_control.fAllowWatchOnly);
                nBytes = tx_sizes.first;
                if (nBytes < 0) {
                    error = _("Signing transaction failed");
                    return false;
                }
                nFeeNeeded = GetMinimumFee(*this, nBytes, coin_control, &feeCalc);
                if (feeCalc.reason == FeeReason::FALLBACK && !m_allow_fallback_fee) {
                    
                    error = _("Fee estimation failed. Fallbackfee is disabled. Wait a few blocks or enable -fallbackfee.");
                    return false;