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?
bool fGood = true;
    {
        LOCK2(cs_main, pwallet->cs_wallet);
        EnsureWalletIsUnlocked(pwallet);
        std::ifstream file;
        file.open(request.params[0].get_str().c_str(), std::ios::in | std::ios::ate);
        if (!file.is_open()) {
            throw JSONRPCError(RPC_INVALID_PARAMETER, "Cannot open wallet dump file");
        }
        nTimeBegin = chainActive.Tip()->GetBlockTime();
        int64_t nFilesize = std::max((int64_t)1, (int64_t)file.tellg());
        file.seekg(0, file.beg);
        
        
        uiInterface.ShowProgress(_("Importing..."), 0, false); 
        while (file.good()) {
            uiInterface.ShowProgress("", std::max(1, std::min(99, (int)(((double)file.tellg() / (double)nFilesize) * 100))), false);
            std::string line;
            std::getline(file, line);
            if (line.empty() || line[0] == '#')
                continue;
            std::vector<std::string> vstr;
            boost::split(vstr, line, boost::is_any_of(" "));
            if (vstr.size() < 2)
                continue;
            CKey key = DecodeSecret(vstr[0]);
            if (key.IsValid()) {
                CPubKey pubkey = key.GetPubKey();
                assert(key.VerifyPubKey(pubkey));
                CKeyID keyid = pubkey.GetID();