class Browser(object):
    options = {
        ...
    }
 
    def fetch(self, url, data=None):
        def setoptDict(curlObj, optDict):
            for optName, optValue in optDict.iteritems():
                curlObj.setopt(getattr(pycurl, optName), optValue)

        buf = StringIO()
        headers =  StringIO()
        curl =  pycurl.Curl()
        
        curl.setopt(pycurl.URL, str(url))
        curl.setopt(pycurl.WRITEFUNCTION, buf.write)
        curl.setopt(pycurl.HEADERFUNCTION, headers.write)
        setoptDict(curl, self.options)

        curl.perform()

        return buf.getvalue()

    def asyncFetch(self, *args, **kwargs):
        return deferToThread(self.fetch, *args, **kwargs)