annoying warning output when QWebView load QNetworkRequest

When I use QWebView instance to load customized QNetworkRequest instance, the console outputs lots of annoying warning like that: 'QObject::connect: Cannot connect (null)::stateChanged(QNetworkSession::State) to QNetworkReplyHttpImpl::_q_networkSessionStateChanged(QNetworkSession::State)'. All just look like running normally, but I don't know why it prints that. I think this will be a problem.

attachment is my python example file.