@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 
warnings.push_back("All private keys are provided, outputs will be considered spendable. If this is intentional, do not specify the watchonly flag.");
            }
            
            if (error.empty()) {
                for (const auto& require_key : import_data.used_keys) {
                    if (!require_key.second) continue; 
                    if (pubkey_map.count(require_key.first) == 0 && privkey_map.count(require_key.first) == 0) {
                        error = "some required keys are missing";
                    }
                }
            }
            if (!error.empty()) {
                warnings.push_back("Importing as non-solvable: " + error + ". If this is intentional, don't provide any keys, pubkeys, witnessscript, or redeemscript.");
                import_data = ImportData();
                pubkey_map.clear();
                privkey_map.clear();
                have_solving_data = false;
            } else {
                
                if (import_data.redeemscript) warnings.push_back("Ignoring redeemscript as this is not a P2SH script.");
                if (import_data.witnessscript) warnings.push_back("Ignoring witnessscript as this is not a (P2SH-)P2WSH script.");
                for (auto it = privkey_map.begin(); it != privkey_map.end(); ) {
                    auto oldit = it++;
                    if (import_data.used_keys.count(oldit->first) == 0) {
                        warnings.push_back("Ignoring irrelevant private key.");
                        privkey_map.erase(oldit);
                    }
                }
                for (auto it = pubkey_map.begin(); it != pubkey_map.end(); ) {
                    auto oldit = it++;