Django AbstractBaseUserでのカスタムユーザの必要設定 (AssertionErrorが発生します。)

Question

Djangoにてカスタムユーザーを定義し、
ログイン認証はallauthを利用しておりますが、実行時（アクセス時）にAssertionErrorが発生します。
（現状、個人的にテストクラスを用意していない。　エラー詳細がNo exception message suppliedと表示されているため、ここで発せられるAssertionErrorは　もともとDjangoに組み込まれていた内容に未設定があるため、発せられてるものと推測します。）
settings.pyにカスタムユーザの仕様を設定する必要がありそうなのですが、現状設定しているものからの不足分が調べてもわかりかねました。（もしくはカスタムユーザーのオーバーライドに不足がある？）
問題解決へお力添え頂きたく、どうぞよろしくお願いします。

【エラーメッセージ】
AssertionError at /accounts/login/
No exception message supplied
Request Method:	GET
Request URL:	http://localhost:8000/accounts/login/
Django Version:	3.1
Exception Type:	AssertionError
Exception Location:	C:\Users\husah\paperwork_system\lib\site-packages\allauth\account\forms.py, line 127, in __init__
Python Executable:	C:\Users\husah\paperwork_system\Scripts\python.exe
Python Version:	3.8.2
Python Path:	
['C:\Users\husah\Dropbox\見積システム\paperwork_system',
 'C:\Users\husah\AppData\Local\Programs\Python\Python38\python38.zip',
 'C:\Users\husah\AppData\Local\Programs\Python\Python38\DLLs',
 'C:\Users\husah\AppData\Local\Programs\Python\Python38\lib',
 'C:\Users\husah\AppData\Local\Programs\Python\Python38',
 'C:\Users\husah\paperwork_system',
 'C:\Users\husah\paperwork_system\lib\site-packages']
Server time:	Wed, 30 Sep 2020 15:37:57 +0900
Traceback Switch to copy-and-paste view
C:\Users\husah\paperwork_system\lib\site-packages\django\core\handlers\exception.py, line 47, in inner
                response = get_response(request) …
▶ Local vars
C:\Users\husah\paperwork_system\lib\site-packages\django\core\handlers\base.py, line 179, in _get_response
                response = wrapped_callback(request, *callback_args, **callback_kwargs) …
▶ Local vars
C:\Users\husah\paperwork_system\lib\site-packages\django\views\generic\base.py, line 73, in view
            return self.dispatch(request, *args, **kwargs) …
▶ Local vars
C:\Users\husah\paperwork_system\lib\site-packages\django\utils\decorators.py, line 43, in _wrapper
        return bound_method(*args, **kwargs) …
▶ Local vars
C:\Users\husah\paperwork_system\lib\site-packages\django\views\decorators\debug.py, line 89, in sensitive_post_parameters_wrapper
            return view(request, *args, **kwargs) …
▶ Local vars
C:\Users\husah\paperwork_system\lib\site-packages\allauth\account\views.py, line 138, in dispatch
        return super(LoginView, self).dispatch(request, *args, **kwargs) …
▶ Local vars
C:\Users\husah\paperwork_system\lib\site-packages\allauth\account\views.py, line 78, in dispatch
            response = super(RedirectAuthenticatedUserMixin, …
▶ Local vars
C:\Users\husah\paperwork_system\lib\site-packages\django\views\generic\base.py, line 101, in dispatch
        return handler(request, *args, **kwargs) …
▶ Local vars
C:\Users\husah\paperwork_system\lib\site-packages\allauth\account\views.py, line 94, in get
        response = super(AjaxCapableProcessFormViewMixin, self).get( …
▶ Local vars
C:\Users\husah\paperwork_system\lib\site-packages\django\views\generic\edit.py, line 133, in get
        return self.render_to_response(self.get_context_data()) …
▶ Local vars
C:\Users\husah\paperwork_system\lib\site-packages\allauth\account\views.py, line 163, in get_context_data
        ret = super(LoginView, self).get_context_data(**kwargs) …
▶ Local vars
C:\Users\husah\paperwork_system\lib\site-packages\django\views\generic\edit.py, line 66, in get_context_data
            kwargs['form'] = self.get_form() …
▶ Local vars
C:\Users\husah\paperwork_system\lib\site-packages\allauth\account\views.py, line 113, in get_form
            form = super(AjaxCapableProcessFormViewMixin, self).get_form( …
▶ Local vars
C:\Users\husah\paperwork_system\lib\site-packages\django\views\generic\edit.py, line 33, in get_form
        return form_class(**self.get_form_kwargs()) …
▶ Local vars
C:\Users\husah\paperwork_system\lib\site-packages\allauth\account\forms.py, line 127, in __init__
            assert app_settings.AUTHENTICATION_METHOD \ …
▶ Local vars

実際のソースコード（modelsとsettings）は以下のとおりです。

【accounts\models.py】
from django.db import models
from django.contrib.auth.base_user import BaseUserManager
from django.contrib.auth.base_user import AbstractBaseUser
from django.contrib.auth.models import PermissionsMixin
from django.contrib.auth.validators import UnicodeUsernameValidator
from django.utils.translation import gettext_lazy as _
from django.utils import timezone


class Users_manager(BaseUserManager):
    use_in_migrations = True

    def _create_user(self, user_id, password, name,**extra_fields):
        if not user_id:
            raise ValueError('The given user_id must be set')
        user_id = self.model.normalize_user_id(user_id)
        user = self.model(user_id=user_id, name=name, **extra_fields)
        user.set_password(password)
        user.save(using=self._db)
        return user

    def create_user(self, user_id, password=None, name=None, **extra_fields):
        extra_fields.setdefault('is_active', False)
        extra_fields.setdefault('is_superuser', False)
        return self._create_user(user_id, password, name, **extra_fields)

    def create_superuser(self, user_id, password=None, name=None, **extra_fields):
        # extra_fields.setdefault('is_staff', True)
        extra_fields.setdefault('is_superuser', True)

        # if extra_fields.get('is_staff') is not True:
        #     raise ValueError('Superuser must have is_staff=True.')
        if extra_fields.get('is_superuser') is not True:
            raise ValueError('Superuser must have is_superuser=True.')

        return self._create_user(user_id, password, name, **extra_fields)

    def with_perm(self, perm, is_active=True, include_superusers=True, backend=None, obj=None):
        if backend is None:
            backends = auth._get_backends(return_tuples=True)
            if len(backends) == 1:
                backend, _ = backends[0]
            else:
                raise ValueError(
                    'You have multiple authentication backends configured and '
                    'therefore must provide the `backend` argument.'
                )
        elif not isinstance(backend, str):
            raise TypeError(
                'backend must be a dotted import path string (got %r).'
                % backend
            )
        else:
            backend = auth.load_backend(backend)
        if hasattr(backend, 'with_perm'):
            return backend.with_perm(
                perm,
                is_active=is_active,
                include_superusers=include_superusers,
                obj=obj,
            )
        return self.none()





class Users(AbstractBaseUser, PermissionsMixin):
    userid_validator = UnicodeUsernameValidator()

    user_id = models.CharField(
        primary_key=True,
        max_length=255,
        validators=[userid_validator],
        error_messages={
            'unique': _("A user with that user_id already exists."),# 要確認　from django.utils.translation import gettext_lazy as _
        },
    )
    name = models.CharField(max_length=255)
    is_active = models.BooleanField(
        _('active'),
        default=True,
        help_text=_(
            'Designates whether this user should be treated as active. '
            'Unselect this instead of deleting accounts.'
        ),
    )
    date_joined = models.DateTimeField(_('date joined'), default=timezone.now)



    objects = Users_manager()

    USERNAME_FIELD = 'user_id'
    REQUIRED_FIELDS = ['name']#  ['user_id','name']  REQUIRED_FIELDSは必須を定義しているが、USERNAME_FIELDで定義してある場合は不要っぽい？





    class meta:
        verbose_name_plural = 'Users'

    def get_name(self):
        return self.name

【settings.py】

#略

INSTALLED_APPS = [
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',

    'paperwork_system',
    'top',
    'client',
    'quotation',

    'accounts.apps.AccountsConfig',
    'django.contrib.sites',
    'allauth',
    'allauth.account',
    'allauth.socialaccount',#allauth\templates\account\login.html（デフォルトのlogin）を利用する際に必要
]

########略 以下カスタムユーザーにかかわる設定#############
AUTH_USER_MODEL = 'accounts.Users'

#django-allauthで利用するdjango.contrib.sitesを使うためのサイト識別用ID
SITE_ID = 1

AUTHENTICATION_BACKENDS = (
'allauth.account.auth_backends.AuthenticationBackend',
'django.contrib.auth.backends.ModelBackend',
)#不要の可能性あり?


ACCOUNT_AUTHENTICATION_METHOD = 'user_id'
ACCOUNT_USERNAME_REQUIRED = False
ACCOUNT_EMAIL_REQUIRED = False
ACCOUNT_USER_MODEL_USERNAME_FIELD = None


LOGIN_REDIRECT_URL = '/top'
ACCOUNT_LOGOUT_REDIRECT_URL = 'accounts/login'

ACCOUNT_LOGOUT_ON_GET = True

MEDIA_ROOT = os.path.join(BASE_DIR,'media')
MEDIA_URL = '/media/'