          clean_username method.
          """
          backend_str = request.session[auth.BACKEND_SESSION_KEY]
          backend = auth.load_backend(backend_str)
          with suppress(AttributeError):  # Backend has no clean_username method.
              username = backend.clean_username(username)
          return username
  
      def _remove_invalid_user(self, request):
          """
 
</s> remove     with suppress(AttributeError):
 </s> add     try: </s> remove     with suppress(Exception):
 </s> add     try:
        try:
          clean_username method.
          """
          backend_str = request.session[auth.BACKEND_SESSION_KEY]
          backend = auth.load_backend(backend_str)
        try:
              username = backend.clean_username(username)
          return username
  
      def _remove_invalid_user(self, request):
          """
keep keep keep keep replace keep keep keep keep keep
 Reverted "Fixed #27818 -- Replaced try/except/pass with contextlib.suppress()."

This reverts commit 550cb3a365dee4edfdd1563224d5304de2a57fda
because try/except performs better. 
django/contrib/auth/middleware.py