WebPage Event that occurs on webpage errors

def onerror(self, emitter, message, source, lineno, colno):
        """ WebPage Event that occurs on webpage errors
        """
        self._log.debug("""App.onerror event occurred in webpage: 
            \nMESSAGE:%s\nSOURCE:%s\nLINENO:%s\nCOLNO:%s\n"""%(message, source, lineno, colno))