AttributeError at /logout/ 'tuple' object has no attribute 'backend' - python-3.x

Question

I used Python3 in windows 10 to write a django2 web app.
I tried to configure the LDAP login, but failed.
When I test using postman, it could get the reply successfully.
That is, I send a request to https://example.com/staff, with some authentication code and payload containing username and password, and it reply me with the LDAP reply.
However, when I tried to using ldap3 in Django, after successfully login, error shows:
AttributeError at /logout/
'tuple' object has no attribute 'backend'
code:
settings.py:
AUTHENTICATION_BACKENDS = (
'app.backends.LDAPBackend',
('django.contrib.auth.backends.ModelBackend'),
)
app/backends.py:
from django.contrib.auth import get_user_model
UserModel = get_user_model()
class LDAPBackend:
def authenticate(self, request, username=None, password=None, **kwargs):
try:
headers = {'Authorization': xxxxx}
body = {"username": username, "password": password}
response = requests.post(url="https://example.com/staff", json=body, headers=headers)
result = response.json()
print(result)
if result['code'] != "OK":
logger.info("Wrong Login Information")
return None
print("connected")
except Exception as e:
print(e)
user = UserModel.objects.update_or_create(username=username)
return user
def get_user(self, user_id):
try:
return UserModel._default_manager.get(pk=user_id)
except UserModel.DoesNotExist:
return None
error shows: AttributeError at /logout/ 'tuple' object has no attribute 'backend', below shows result in console:
connected
Internal Server Error: /logout/
Traceback (most recent call last):
File "C:\Users\software\python\lib\site-packages\django\core\handlers\exception.py", line 34, in inner
response = get_response(request)
File "C:\Users\software\python\lib\site-packages\django\core\handlers\base.py", line 115, in _get_response
response = self.process_exception_by_middleware(e, request)
File "C:\Users\software\python\lib\site-packages\django\core\handlers\base.py", line 113, in _get_response
response = wrapped_callback(request, *callback_args, **callback_kwargs)
File "C:\Users\software\python\lib\site-packages\django\views\generic\base.py", line 71, in view
return self.dispatch(request, *args, **kwargs)
File "C:\Users\software\python\lib\site-packages\django\utils\decorators.py", line 45, in _wrapper
return bound_method(*args, **kwargs)
File "C:\Users\software\python\lib\site-packages\django\views\decorators\debug.py", line 76, in sensitive_post_parameters_wrapper
return view(request, *args, **kwargs)
File "C:\Users\software\python\lib\site-packages\django\utils\decorators.py", line 45, in _wrapper
return bound_method(*args, **kwargs)
File "C:\Users\software\python\lib\site-packages\django\utils\decorators.py", line 142, in _wrapped_view
response = view_func(request, *args, **kwargs)
File "C:\Users\software\python\lib\site-packages\django\utils\decorators.py", line 45, in _wrapper
return bound_method(*args, **kwargs)
File "C:\Users\software\python\lib\site-packages\django\views\decorators\cache.py", line 44, in _wrapped_view_func
response = view_func(request, *args, **kwargs)
File "C:\Users\software\python\lib\site-packages\django\contrib\auth\views.py", line 61, in dispatch
return super().dispatch(request, *args, **kwargs)
File "C:\Users\software\python\lib\site-packages\django\views\generic\base.py", line 97, in dispatch
return handler(request, *args, **kwargs)
File "C:\Users\software\python\lib\site-packages\django\views\generic\edit.py", line 141, in post
if form.is_valid():
File "C:\Users\software\python\lib\site-packages\django\forms\forms.py", line 185, in is_valid
return self.is_bound and not self.errors
File "C:\Users\software\python\lib\site-packages\django\forms\forms.py", line 180, in errors
self.full_clean()
File "C:\Users\software\python\lib\site-packages\django\forms\forms.py", line 382, in full_clean
self._clean_form()
File "C:\Users\software\python\lib\site-packages\django\forms\forms.py", line 409, in _clean_form
cleaned_data = self.clean()
File "C:\Users\software\python\lib\site-packages\django\contrib\auth\forms.py", line 205, in clean
self.user_cache = authenticate(self.request, username=username, password=password)
File "C:\Users\software\python\lib\site-packages\django\contrib\auth\__init__.py", line 80, in authenticate
user.backend = backend_path
AttributeError: 'tuple' object has no attribute 'backend'
[22/Mar/2021 09:49:10] "POST /logout/ HTTP/1.1" 500 149071

Answer 1

You write the following line:
user = UserModel.objects.update_or_create(username=username)
The update_or_create method returns a tuple with the object and a boolean with whether the object was created. So you are storing this tuple in the variable user and returning that. But authenticate is supposed to return only the user causing unintended effects leading to an error. Also you should be using get_or_create [Django docs] instead of update_or_create.
So you should change that above line to:
user, created = UserModel.objects.get_or_create(username=username)