before if sreg sreg join arg for arg in sreg split if arg nickname or

# before

                if sreg:
                    sreg = ','.join([arg for arg in sreg.split(',') if arg != 'nickname' or arg != 'email'])
                extension_args['sreg.optional'] = 'email,nickname'
            if sreg:
                extension_args['sreg.optional'] += ',' + sreg

#after

        sreg = set(self.sreg.split(',')).union(['email', 'nickname'])
        self.extendsion_args['sreg.optional'] = ','.join(sreg)