Django Wagtail博客示例导致没有属性'_默认管理器'；

我正在使用Python3.6.7、Wagtail 2.5.1和Django 2.2.1完成这项工作。在我在页面末尾添加类别之前，一切正常

class ArticlePage(Page):
    date = models.DateField("Post date")
    intro = models.CharField(max_length=250)
    body = RichTextField(blank=True)
    tags = ClusterTaggableManager(through=ArticlePageTag, blank=True)
    categories = ParentalManyToManyField('article.ArticleCategory', blank=True)

# ... (Keep the main_image method and search_fields definition)

content_panels = Page.content_panels + [
    MultiFieldPanel([
        FieldPanel('date'),
        FieldPanel('tags'),
        FieldPanel('categories', widget=forms.CheckboxSelectMultiple),
    ], heading="Article information"),
    FieldPanel('intro'),
    FieldPanel('body'),
    InlinePanel('gallery_images', label="Gallery images"),
]

FieldPanel“categories”产生错误。以下是运行makemigrations时的回溯：

(env) simon@ckweb$ ./manage.py makemigrations                                                                                                                    │Watching for file changes with StatReloader
Traceback (most recent call last):                                                                                                                               │Exception in thread django-main-thread:
  File "./manage.py", line 10, in <module>                                                                                                                       │Traceback (most recent call last):
    execute_from_command_line(sys.argv)                                                                                                                          │  File "/usr/lib/python3.6/threading.py", line 916, in _bootstrap_inner
  File "/home/simon/.local/lib/python3.6/site-packages/django/core/management/__init__.py", line 381, in execute_from_command_line                               │    self.run()
    utility.execute()                                                                                                                                            │  File "/usr/lib/python3.6/threading.py", line 864, in run
  File "/home/simon/.local/lib/python3.6/site-packages/django/core/management/__init__.py", line 375, in execute                                                 │    self._target(*self._args, **self._kwargs)
    self.fetch_command(subcommand).run_from_argv(self.argv)                                                                                                      │  File "/home/simon/.local/lib/python3.6/site-packages/django/utils/autoreload.py", line 54, in wrapper
  File "/home/simon/.local/lib/python3.6/site-packages/django/core/management/base.py", line 323, in run_from_argv                                               │    fn(*args, **kwargs)
    self.execute(*args, **cmd_options)                                                                                                                           │  File "/home/simon/.local/lib/python3.6/site-packages/django/core/management/commands/runserver.py", line 109, in inner_run
  File "/home/simon/.local/lib/python3.6/site-packages/django/core/management/base.py", line 361, in execute                                                     │    autoreload.raise_last_exception()
    self.check()                                                                                                                                                 │  File "/home/simon/.local/lib/python3.6/site-packages/django/utils/autoreload.py", line 77, in raise_last_exception
  File "/home/simon/.local/lib/python3.6/site-packages/django/core/management/base.py", line 390, in check                                                       │    raise _exception[0](_exception[1]).with_traceback(_exception[2])
    include_deployment_checks=include_deployment_checks,                                                                                                         │  File "/home/simon/.local/lib/python3.6/site-packages/django/utils/autoreload.py", line 54, in wrapper
  File "/home/simon/.local/lib/python3.6/site-packages/django/core/management/base.py", line 377, in _run_checks                                                 │    fn(*args, **kwargs)
    return checks.run_checks(**kwargs)                                                                                                                           │  File "/home/simon/.local/lib/python3.6/site-packages/django/__init__.py", line 24, in setup
  File "/home/simon/.local/lib/python3.6/site-packages/django/core/checks/registry.py", line 72, in run_checks                                                   │    apps.populate(settings.INSTALLED_APPS)
    new_errors = check(app_configs=app_configs)                                                                                                                  │  File "/home/simon/.local/lib/python3.6/site-packages/django/apps/registry.py", line 114, in populate
  File "/home/simon/.local/lib/python3.6/site-packages/wagtail/admin/checks.py", line 63, in get_form_class_check                                                │    app_config.import_models()
    if not issubclass(edit_handler.get_form_class(), WagtailAdminPageForm):                                                                                      │  File "/home/simon/.local/lib/python3.6/site-packages/django/apps/config.py", line 211, in import_models
  File "/home/simon/.local/lib/python3.6/site-packages/wagtail/admin/edit_handlers.py", line 369, in get_form_class                                              │    self.models_module = import_module(models_module_name)
    widgets=self.widget_overrides())                                                                                                                             │  File "/usr/lib/python3.6/importlib/__init__.py", line 126, in import_module
  File "/home/simon/.local/lib/python3.6/site-packages/wagtail/admin/edit_handlers.py", line 64, in get_form_for_model                                           │    return _bootstrap._gcd_import(name[level:], package, level)
    return metaclass(class_name, (form_class,), form_class_attrs)                                                                                                │  File "<frozen importlib._bootstrap>", line 994, in _gcd_import
  File "/home/simon/.local/lib/python3.6/site-packages/wagtail/admin/forms/models.py", line 66, in __new__                                                       │  File "<frozen importlib._bootstrap>", line 971, in _find_and_load
    new_class = super(WagtailAdminModelFormMetaclass, cls).__new__(cls, name, bases, attrs)                                                                      │  File "<frozen importlib._bootstrap>", line 955, in _find_and_load_unlocked
  File "/home/simon/.local/lib/python3.6/site-packages/modelcluster/forms.py", line 245, in __new__                                                              │  File "<frozen importlib._bootstrap>", line 665, in _load_unlocked
    new_class = super(ClusterFormMetaclass, cls).__new__(cls, name, bases, attrs)                                                                                │  File "<frozen importlib._bootstrap_external>", line 678, in exec_module
  File "/home/simon/.local/lib/python3.6/site-packages/django/forms/models.py", line 256, in __new__                                                             │  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
    apply_limit_choices_to=False,                                                                                                                                │  File "/mnt/c/Users/simon/OneDrive/dev/wagtail/ckweb/articles/models.py", line 33, in <module>
  File "/home/simon/.local/lib/python3.6/site-packages/django/forms/models.py", line 176, in fields_for_model                                                    │    class ArticlePage(Page):
    formfield = formfield_callback(f, **kwargs)                                                                                                                  │  File "/mnt/c/Users/simon/OneDrive/dev/wagtail/ckweb/articles/models.py", line 58, in ArticlePage
  File "/home/simon/.local/lib/python3.6/site-packages/wagtail/admin/forms/models.py", line 47, in formfield_for_dbfield                                         │    InlinePanel('related_content_page', widget=forms.CheckboxSelectMultiple),
    return db_field.formfield(**kwargs)                                                                                                                          │  File "/home/simon/.local/lib/python3.6/site-packages/wagtail/admin/edit_handlers.py", line 646, in __init__
  File "/home/simon/.local/lib/python3.6/site-packages/django/db/models/fields/related.py", line 1626, in formfield                                              │    super().__init__(*args, **kwargs)
    'queryset': self.remote_field.model._default_manager.using(using),                                                                                           │TypeError: __init__() got an unexpected keyword argument 'widget'
AttributeError: 'str' object has no attribute '_default_manager'

（env）simon@ckweb$./manage.py makemigrations│使用StatReloader监视文件更改
回溯（最近一次呼叫最后一次）：│线程django主线程中出现异常：
文件“/manage.py”，第10行，在│回溯（最近一次呼叫最后一次）：
从命令行（sys.argv）执行命令│  文件“/usr/lib/python3.6/threading.py”，第916行，在内部引导中
文件“/home/simon/.local/lib/python3.6/site packages/django/core/management/_init__.py”，第381行，从命令行执行│    self.run（）
utility.execute（）│  文件“/usr/lib/python3.6/threading.py”，第864行，运行中
文件“/home/simon/.local/lib/python3.6/site packages/django/core/management/_init__.py”，执行中第375行│    自我目标（*自我参数，**自我参数）
self.fetch_命令（子命令）。从_argv（self.argv）运行_│  文件“/home/simon/.local/lib/python3.6/site packages/django/utils/autoreload.py”，第54行，在包装器中
文件“/home/simon/.local/lib/python3.6/site packages/django/core/management/base.py”，第323行，在运行时从│    fn（*args，**kwargs）
self.execute（*args，**cmd_选项）│  文件“/home/simon/.local/lib/python3.6/site packages/django/core/management/commands/runserver.py”，第109行，在内部运行
文件“/home/simon/.local/lib/python3.6/site packages/django/core/management/base.py”，第361行，在execute中│    autoreload.raise\u last\u异常（）
self.check（）│  文件“/home/simon/.local/lib/python3.6/site packages/django/utils/autoreload.py”，第77行，在raise\u last\u异常中
文件“/home/simon/.local/lib/python3.6/site packages/django/core/management/base.py”，第390行，选中│    引发异常[0]（\u异常[1]）。并进行跟踪（\u异常[2]）
包括部署检查=包括部署检查，│  文件“/home/simon/.local/lib/python3.6/site packages/django/utils/autoreload.py”，第54行，在包装器中
文件“/home/simon/.local/lib/python3.6/site packages/django/core/management/base.py”，第377行，在运行检查中│    fn（*args，**kwargs）
返回检查。运行检查（**kwargs）│  文件“/home/simon/.local/lib/python3.6/site packages/django/_init__.py”，第24行，在安装程序中
文件“/home/simon/.local/lib/python3.6/site packages/django/core/checks/registry.py”，第72行，运行检查│    应用程序。填充（设置。已安装的应用程序）
新建错误=检查（应用程序配置=应用程序配置）│  文件“/home/simon/.local/lib/python3.6/site packages/django/apps/registry.py”，第114行，填充
文件“/home/simon/.local/lib/python3.6/site packages/wagtail/admin/checks.py”，第63行，在get\u form\u class\u check中│    app_config.import_models（）
如果不是issubclass（编辑\u handler.get\u form\u class（），WagtailAdminPageForm）：│  文件“/home/simon/.local/lib/python3.6/site packages/django/apps/config.py”，第211行，在import\u模型中
文件“/home/simon/.local/lib/python3.6/site packages/wagtail/admin/edit\u handlers.py”，第369行，在get\u form\u类中│    self.models\u module=导入模块（models\u module\u name）
widgets=self.widget\u覆盖（）│  文件“/usr/lib/python3.6/importlib/_init_uuu.py”，第126行，在导入模块中
文件“/home/simon/.local/lib/python3.6/site packages/wagtail/admin/edit_handlers.py”，第64行，在get_form_for_模型中│    return _bootstrap._gcd_import（名称[级别：]，包，级别）
返回元类（类名称，（形式类），形式类属性）│  文件“”，第994行，在_gcd_导入中
文件“/home/simon/.local/lib/python3.6/site packages/wagtail/admin/forms/models.py”，第66行，在│  文件“”
ParentalManyToManyField('article.ArticleCategory', blank=True)

ParentalManyToManyField('articles.ArticleCategory', blank=True)