Identify to NickServ (legacy).

def nickserv_identify(self, password, use_nick=None):
        """Identify to NickServ (legacy)."""
        if self.ready:
            if use_nick:
                self.msg(use_nick, 'IDENTIFY {}'.format(password))
            else:
                self.send('NICKSERV', params=['IDENTIFY', password])
        else:
            self.connect_info['nickserv'] = {
                'password': password,
                'use_nick': use_nick,
            }