In the log I see things like:

    2017-09-13 03:54:33 init message: Rescanning...
    2017-09-13 03:54:33 Rescanning last 68616 blocks (from block 416339)...
    2017-09-13 03:54:40 AddToWallet xxxxx  update
    2017-09-13 03:55:33 Still rescanning. At block 418849. Progress=0.549138

I would be interested to see the wallet file name on each of these log lines.

Would there be any interest in merging such a PR?
if (fRescan && !reserver.reserve()) {
        throw JSONRPCError(RPC_WALLET_ERROR, "Wallet is currently rescanning. Abort existing rescan or wait.");
    }
    
    bool fP2SH = false;
    if (!request.params[3].isNull())
        fP2SH = request.params[3].get_bool();
    {
        LOCK2(cs_main, pwallet->cs_wallet);
        CTxDestination dest = DecodeDestination(request.params[0].get_str());
        if (IsValidDestination(dest)) {
            if (fP2SH) {
                throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Cannot use the p2sh flag with an address - use a script instead");
            }
            ImportAddress(pwallet, dest, strLabel);
        } else if (IsHex(request.params[0].get_str())) {
            std::vector<unsigned char> data(ParseHex(request.params[0].get_str()));
            ImportScript(pwallet, CScript(data.begin(), data.end()), strLabel, fP2SH);
        } else {
            throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Invalid Bitcoin address or script");
        }
    }
    if (fRescan)
    {
        RescanWallet(*pwallet, reserver);
        pwallet->ReacceptWalletTransactions();
    }
    return NullUniValue;
}
UniValue importprunedfunds(const JSONRPCRequest& request)