Load rules from YAML configuration in the given stream object
        :param filename: Filename of rule YAML file
        :return: rules object

def load_rules(self, filename):
        """
        Load rules from YAML configuration in the given stream object
        :param filename: Filename of rule YAML file
        :return: rules object
        """
        self.logger.debug('Reading rules from %s', filename)
        try:
            in_file = open(filename)
        except IOError:
            self.logger.error('Error opening {0}'.format(filename))
            raise

        y = None
        try:
            y = yaml.load(in_file)
        except yaml.YAMLError as exc:
            if hasattr(exc, 'problem_mark'):
                self.logger.error('Error parsing rules{0}'.format(exc.problem_mark))

            else:
                self.logger.error('Error parsing rules in {0}'.format(in_file.name))
            raise
        return y