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 (pwallet->HaveKey(keyid)) {
                    LogPrintf("Skipping import of %s (key already present)\n", EncodeDestination(keyid));
                    continue;
                }
                int64_t nTime = DecodeDumpTime(vstr[1]);
                std::string strLabel;
                bool fLabel = true;
                for (unsigned int nStr = 2; nStr < vstr.size(); nStr++) {
                    if (vstr[nStr].front() == '#')
                        break;
                    if (vstr[nStr] == "change=1")
                        fLabel = false;
                    if (vstr[nStr] == "reserve=1")
                        fLabel = false;
                    if (vstr[nStr].substr(0,6) == "label=") {
                        strLabel = DecodeDumpString(vstr[nStr].substr(6));
                        fLabel = true;
                    }
                }
                LogPrintf("Importing %s...\n", EncodeDestination(keyid));
                if (!pwallet->AddKeyPubKey(key, pubkey)) {
                    fGood = false;
                    continue;
                }
                pwallet->mapKeyMetadata[keyid].nCreateTime = nTime;
                if (fLabel)
                    pwallet->SetAddressBook(keyid, strLabel, "receive");
                nTimeBegin = std::min(nTimeBegin, nTime);
            } else if(IsHex(vstr[0])) {
               std::vector<unsigned char> vData(ParseHex(vstr[0]));