Parse a chance element
        :param element: The XML Element object
        :type  element: etree._Element

def _parse_chance(self, element):
        """
        Parse a chance element
        :param element: The XML Element object
        :type  element: etree._Element
        """
        try:
            chance = float(element.text)
        except (ValueError, TypeError, AttributeError):
            self._log.warn('Invalid Chance string: {chance}'.format(chance=element.text))
            return

        # Make sure the chance is a valid percentage
        if not (0 <= chance <= 100):
            self._log.warn('Chance percent must contain an integer or float between 0 and 100')
            return

        self.chance = chance
        self.chance_blocking = bool_attribute(element, 'blocking', self.chance_blocking)