Install Qt translator to the QApplication instance

def install_translator(qapp):
    """Install Qt translator to the QApplication instance"""
    global QT_TRANSLATOR
    if QT_TRANSLATOR is None:
        qt_translator = QTranslator()
        if qt_translator.load("qt_"+QLocale.system().name(),
                      QLibraryInfo.location(QLibraryInfo.TranslationsPath)):
            QT_TRANSLATOR = qt_translator # Keep reference alive
    if QT_TRANSLATOR is not None:
        qapp.installTranslator(QT_TRANSLATOR)