QtWebkit python crash on windows

I am trying to clean up a site that uses javascript. I am using the following code:

import os
import sys
import re
import requests
import mechanize
import cookielib
from bs4 import BeautifulSoup
from PyQt4.QtGui import *  
from PyQt4.QtCore import *  
from PyQt4.QtWebKit import *  
from lxml import html
import pandas as pd
import time

class Render(QWebPage):
    def __init__(self, url):
        self.app = QApplication(sys.argv)
        QWebPage.__init__(self)
        self.loadFinished.connect(self._loadFinished)
        self.mainFrame().load(QUrl(url))
        self.app.exec_()


    def _loadFinished(self, result):
        self.frame = self.mainFrame()
        self.app.quit()

def read_page(url):
    r = Render(url)
    result = r.frame.toHtml()
    text = str(result.toAscii())
    html_source = html.fromstring(text)
    return text, html_source

for url in urls:
    text, html_source = read_page(url)

      

        
        
        
      

    

After successfully reading the first url, the following message appears on the second url and python.exe crashes.

content-type missing in HTTP POST, defaulting to application/x-www-form-urlencoded. Use QNetworkRequest::setHeader() to fix this problem.
QObject::connect: Cannot connect (null)::configurationAdded(QNetworkConfiguration) to QNetworkConfigurationManager::configurationAdded(QNetworkConfiguration)
QObject::connect: Cannot connect (null)::configurationRemoved(QNetworkConfiguration) to QNetworkConfigurationManager::configurationRemoved(QNetworkConfiguration)
QObject::connect: Cannot connect (null)::configurationChanged(QNetworkConfiguration) to QNetworkConfigurationManager::configurationChanged(QNetworkConfiguration)
QObject::connect: Cannot connect (null)::onlineStateChanged(bool) to QNetworkConfigurationManager::onlineStateChanged(bool)
QObject::connect: Cannot connect (null)::configurationUpdateComplete() to QNetworkConfigurationManager::updateCompleted()