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?
{
    std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
    CWallet* const pwallet = wallet.get();
    if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
        return NullUniValue;
    }
    if (request.fHelp || request.params.size() < 1 || request.params.size() > 3)
        throw std::runtime_error(
            "importpubkey \"pubkey\" ( \"label\" rescan )\n"
            "\nAdds a public key (in hex) that can be watched as if it were in your wallet but cannot be used to spend. Requires a new wallet backup.\n"
            "\nArguments:\n"
            "1. \"pubkey\"           (string, required) The hex-encoded public key\n"
            "2. \"label\"            (string, optional, default=\"\") An optional label\n"
            "3. rescan               (boolean, optional, default=true) Rescan the wallet for transactions\n"
            "\nNote: This call can take minutes to complete if rescan is true, during that time, other rpc calls\n"
            "may report that the imported pubkey exists but related transactions are still missing, leading to temporarily incorrect/bogus balances and unspent outputs until rescan completes.\n"
            "\nExamples:\n"
            "\nImport a public key with rescan\n"
            + HelpExampleCli("importpubkey", "\"mypubkey\"") +
            "\nImport using a label without rescan\n"
            + HelpExampleCli("importpubkey", "\"mypubkey\" \"testing\" false") +
            "\nAs a JSON-RPC call\n"
            + HelpExampleRpc("importpubkey", "\"mypubkey\", \"testing\", false")
        );
    std::string strLabel;
    if (!request.params[1].isNull())
        strLabel = request.params[1].get_str();
    
    bool fRescan = true;