code: def verify_ticket(self, ticket):
          
          params = [('ticket', ticket), ('service', self.service_url)]
          if self.renew:
              params.append(('renew', 'true'))
          url = (urllib_parse.urljoin(self.server_url, 'validate') + '?' +
                 urllib_parse.urlencode(params))
          page = urllib_request.urlopen(url)
          try:
              verified = page.readline().strip()
              if verified == b'yes':
                  charset = self.get_page_charset(page, default="ascii")
                  user = self.u(page.readline().strip(), charset)
                  return user, None, None
              else:
                  return None, None, None
          finally:
              page.close()
docs: Verifies CAS 1.0 authentication ticket.
  
          Returns username on success and None on failure.