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?
CScript script = CScript(vData.begin(), vData.end());
               CScriptID id(script);
               if (pwallet->HaveCScript(id)) {
                   LogPrintf("Skipping import of %s (script already present)\n", vstr[0]);
                   continue;
               }
               if(!pwallet->AddCScript(script)) {
                   LogPrintf("Error importing script %s\n", vstr[0]);
                   fGood = false;
                   continue;
               }
               int64_t birth_time = DecodeDumpTime(vstr[1]);
               if (birth_time > 0) {
                   pwallet->m_script_metadata[id].nCreateTime = birth_time;
                   nTimeBegin = std::min(nTimeBegin, birth_time);
               }
            }
        }
        file.close();
        uiInterface.ShowProgress("", 100, false); 
        pwallet->UpdateTimeFirstKey(nTimeBegin);
    }
    uiInterface.ShowProgress("", 100, false); 
    RescanWallet(*pwallet, reserver, nTimeBegin, false );
    pwallet->MarkDirty();
    if (!fGood)
        throw JSONRPCError(RPC_WALLET_ERROR, "Error adding some keys/scripts to wallet");
    return NullUniValue;
}
UniValue dumpprivkey(const JSONRPCRequest& request)