Debugging PyQt5 QSql

Hi

I have challenge finding a bug when calling db.open(), I can't trace the code, anyone who have an idea how to debug QtPy4/5?

Running Win10 64 on Bootcamp Mac Pro , Python 3.6.1

The code for short is

from PyQt5.QtWidgets import QMessageBox
from PyQt5.QtSql import QSqlDatabase
from configparser import RawConfigParser

def createconnection():
    parser = RawConfigParser()
    parser.read('Qtabwindow.cfg')
    result =QSqlDatabase.isDriverAvailable('QMYSQL')
    print(result)
    db = QSqlDatabase.addDatabase('QMYSQL')
    db.setHostName(parser.get("DEFAULT", 'Hostname'))
    db.setDatabaseName(parser.get('DEFAULT', 'DatabaseName'))
    db.setUserName(parser.get('DEFAULT', 'UserName'))
    db.setPassword(parser.get('DEFAULT', 'PassWord'))

    if not db.open():
        '''
        QMessageBox.critical(None, 'Cannot open database \
        Unable to establish a database connection.\
        This example needs SQL support.Please read the Qt SQL',
        QMessageBox.Cancel)
        '''
        return False
    return True