@jonasschnelli wrote in #14979:
> #14573 broke < Qt5.6 compatibility due to calling the lambda version of `addAction` that was added in Qt5.6.

We currently [support](https://github.com/bitcoin/bitcoin/blob/master/doc/dependencies.md) QT >=5.2, but hardly anyone tests with that. If we make one of the Travis machines use it, we should have a better change of catching this.

See also discussion about minimum QT version in #13478 
"\nImport using a label and without rescan\n"
            + HelpExampleCli("importprivkey", "\"mykey\" \"testing\" false") +
            "\nImport using default blank label and without rescan\n"
            + HelpExampleCli("importprivkey", "\"mykey\" \"\" false") +
            "\nAs a JSON-RPC call\n"
            + HelpExampleRpc("importprivkey", "\"mykey\", \"testing\", false")
                },
            }.ToString());
    WalletRescanReserver reserver(pwallet);
    bool fRescan = true;
    {
        auto locked_chain = pwallet->chain().lock();
        LOCK(pwallet->cs_wallet);
        EnsureWalletIsUnlocked(pwallet);
        std::string strSecret = request.params[0].get_str();
        std::string strLabel = "";
        if (!request.params[1].isNull())
            strLabel = request.params[1].get_str();
        
        if (!request.params[2].isNull())
            fRescan = request.params[2].get_bool();
        if (fRescan && fPruneMode)
            throw JSONRPCError(RPC_WALLET_ERROR, "Rescan is disabled in pruned mode");
        if (fRescan && !reserver.reserve()) {
            throw JSONRPCError(RPC_WALLET_ERROR, "Wallet is currently rescanning. Abort existing rescan or wait.");
        }
        CKey key = DecodeSecret(strSecret);
        if (!key.IsValid()) throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Invalid private key encoding");
        CPubKey pubkey = key.GetPubKey();
        assert(key.VerifyPubKey(pubkey));