@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 
std::stringstream ret;
    for (const unsigned char c : str) {
        if (c <= 32 || c >= 128 || c == '%') {
            ret << '%' << HexStr(&c, &c + 1);
        } else {
            ret << c;
        }
    }
    return ret.str();
}
static std::string DecodeDumpString(const std::string &str) {
    std::stringstream ret;
    for (unsigned int pos = 0; pos < str.length(); pos++) {
        unsigned char c = str[pos];
        if (c == '%' && pos+2 < str.length()) {
            c = (((str[pos+1]>>6)*9+((str[pos+1]-'0')&15)) << 4) |
                ((str[pos+2]>>6)*9+((str[pos+2]-'0')&15));
            pos += 2;
        }
        ret << c;
    }
    return ret.str();
}
static bool GetWalletAddressesForKey(CWallet * const pwallet, const CKeyID &keyid, std::string &strAddr, std::string &strLabel)