背景

Djangoのバージョンを1.11.1から2.2へアップデート中、
自分でカスタマイズさせといたauthenticationでエラーが出るようになった。

django1.11.1のauthenticate

https://docs.djangoproject.com/ja/1.11/_modules/django/contrib/auth/

def authenticate(request=None, **credentials):
    """
    If the given credentials are valid, return a User object.
    """
    for backend, backend_path in _get_backends(return_tuples=True):
        try:
            user = _authenticate_with_backend(backend, backend_path, request, credentials)
        except PermissionDenied:
            # This backend says to stop in our tracks - this user should not be allowed in at all.
            break
        if user is None:
            continue
        # Annotate the user object with the path of the backend.
        user.backend = backend_path
        return user

    # The credentials supplied are invalid to all backends, fire signal
    user_login_failed.send(sender=__name__, credentials=_clean_credentials(credentials), request=request)



def _authenticate_with_backend(backend, backend_path, request, credentials):
    args = (request,)
    # Does the backend accept a request argument? <---このコメント何。
    try:
        inspect.getcallargs(backend.authenticate, request, **credentials)
    except TypeError:
        args = ()
        credentials.pop('request', None)
        # Does the backend accept a request keyword argument?
        try:
            inspect.getcallargs(backend.authenticate, request=request, **credentials)
        except TypeError:
            # Does the backend accept credentials without request?
            try:
                inspect.getcallargs(backend.authenticate, **credentials)
            except TypeError:
                # This backend doesn't accept these credentials as arguments. Try the next one.
                return None
            else:
                warnings.warn(
                    "Update %s.authenticate() to accept a positional "
                    "`request` argument." % backend_path,
                    RemovedInDjango21Warning
                )
        else:
            credentials['request'] = request
            warnings.warn(
                "In %s.authenticate(), move the `request` keyword argument "
                "to the first positional argument." % backend_path,
                RemovedInDjango21Warning
            )
    return backend.authenticate(*args, **credentials)

↓自分で作ったauthentication

from django.contrib.auth.backends import ModelBackend
from .models import UserProfile


class SignedRequestBackend(ModelBackend):
    """認証を別途行うため、素通りの認証バックエンドを実装"""

    def authenticate(self, user=None, user_profile=None, **kwds):
        if user is None:
            return
        if not user.is_authenticated or not user.is_active:
            return
        if municipality_user_profile is None:
            return
        if not isinstance(user_profile, UserProfile):
            return
        if user.id != user_profile.user_id:
            return
        return user

django2.2のauthenticate

https://docs.djangoproject.com/ja/2.2/_modules/django/contrib/auth/

def authenticate(request=None, **credentials):
    """
    If the given credentials are valid, return a User object.
    """
    for backend, backend_path in _get_backends(return_tuples=True):
        try:
            inspect.getcallargs(backend.authenticate, request, **credentials)
        except TypeError:
            # This backend doesn't accept these credentials as arguments. Try the next one.
            continue
        try:
            user = backend.authenticate(request, **credentials)
        except PermissionDenied:
            # This backend says to stop in our tracks - this user should not be allowed in at all.
            break
        if user is None:
            continue
        # Annotate the user object with the path of the backend.
        user.backend = backend_path
        return user

    # The credentials supplied are invalid to all backends, fire signal
    user_login_failed.send(sender=__name__, credentials=_clean_credentials(credentials), request=request)

【結論】 _authenticate_with_backend functionが廃止されてます。

inspect.getcallargsをデバッグしてみたところ

https://github.com/python/cpython/blob/3.8/Lib/inspect.py#L1335

【エラー原因】 argsに['self', 'user', 'user_profile']って代入される（ここには['self', 'request']と入ってほしい）

あ、なんかコメントあったな... # Does the backend accept a request argument?
自分で作ったauthenticationの引数にrequestを設定 → エラーが解決されました。