If I create an RBF transaction using the Qt GUI but specify my own custom change address, bumpfee doesn't work because it claims it can't find the change address:

    "Transaction does not have a change output"

This is because none of the outputs satisfy

    pWallet->IsChange(...)

I see there's a "TODO" commented in `CWallet::IsChange()` in `src/wallet/wallet.cpp`:

    // TODO: fix handling of 'change' outputs. The assumption is that any
    // payment to a script that is ours, but is not in the address book
    // is change.

I tend to put all my addresses in the address book whether I'm going to use them as change or not. I guess if the wallet was capable of creating its own SegWit change addresses I'd stop using custom change addresses, but currently it always seems to send change to a legacy address if I don't manually specify a change address.
const CAmount effective_value{total_input_value - fee_from_size};
            if (fee_from_size > pwallet->m_default_max_tx_fee) {
                throw JSONRPCError(RPC_WALLET_ERROR, TransactionErrorString(TransactionError::MAX_FEE_EXCEEDED).original);
            }
            if (effective_value <= 0) {
                if (send_max) {
                    throw JSONRPCError(RPC_WALLET_INSUFFICIENT_FUNDS, "Total value of UTXO pool too low to pay for transaction, try using lower feerate.");
                } else {
                    throw JSONRPCError(RPC_WALLET_INSUFFICIENT_FUNDS, "Total value of UTXO pool too low to pay for transaction. Try using lower feerate or excluding uneconomic UTXOs with 'send_max' option.");
                }
            }
            /
            if (tx_size.weight > MAX_STANDARD_TX_WEIGHT) {
                throw JSONRPCError(RPC_WALLET_ERROR, "Transaction too large.");
            }
            CAmount output_amounts_claimed{0};
            for (const CTxOut& out : rawTx.vout) {
                output_amounts_claimed += out.nValue;
            }
            if (output_amounts_claimed > total_input_value) {
                throw JSONRPCError(RPC_WALLET_INSUFFICIENT_FUNDS, "Assigned more value to outputs than available funds.");
            }
            const CAmount remainder{effective_value - output_amounts_claimed};
            if (remainder < 0) {
                throw JSONRPCError(RPC_WALLET_INSUFFICIENT_FUNDS, "Insufficient funds for fees after creating specified outputs.");
            }
            const CAmount per_output_without_amount{remainder / (long)addresses_without_amount.size()};
            bool gave_remaining_to_first{false};
            for (CTxOut& out : rawTx.vout) {
                CTxDestination dest;