code: def _process_sasl_failure(self, stream, element):
          
          _unused = stream
          if not self.authenticator:
              logger.debug("Unexpected SASL response")
              return False
  
          logger.debug("SASL authentication failed: {0!r}".format(
                                                  element_to_unicode(element)))
          raise SASLAuthenticationFailed("SASL authentication failed")
docs: Process incoming <sasl:failure/> element.
  
          [initiating entity only]