Overwrite the default get_alert method.

        Alert is on signal quality where lower is better...

        :returns: string -- Signal alert

def get_alert(self, value):
        """Overwrite the default get_alert method.

        Alert is on signal quality where lower is better...

        :returns: string -- Signal alert
        """
        ret = 'OK'
        try:
            if value <= self.get_limit('critical', stat_name=self.plugin_name):
                ret = 'CRITICAL'
            elif value <= self.get_limit('warning', stat_name=self.plugin_name):
                ret = 'WARNING'
            elif value <= self.get_limit('careful', stat_name=self.plugin_name):
                ret = 'CAREFUL'
        except (TypeError, KeyError) as e:
            # Catch TypeError for issue1373
            ret = 'DEFAULT'

        return ret