django - インラインで Django admin を介してオブジェクトを追加するときの DoesNotExist 例外

Question

models.py

class Service(models.Model):

    provider = models.ForeignKey("services.ServiceProvider",
                                 verbose_name=_("Service provider"),
                                 related_name="services")
    title = models.CharField(_("Title"), max_length=150)

class Entertainment(Service):

    types = models.ManyToManyField(EntertainmentType, verbose_name=_("Types"),
                                   related_name="entertainments")

    description = models.TextField(_("Description"), blank=True)

class EntertainmentPhoto(models.Model):

    entertainment = models.ForeignKey(Entertainment, related_name="photos")
    description = models.TextField(_("Description"), max_length=1000,
                                   blank=True)
    photo = ImageWithThumbsField(_("Photo"), sizes=(),
                                 upload_to="services/photos/entertainment")
    is_main = models.BooleanField(verbose_name=_("Main"), default=False)

    class Meta:
        ordering = ('-is_main',)
        verbose_name = _("Photo")
        verbose_name_plural = _("Photos")

**admin.py**

class EntertainmentPhotoInline(admin.TabularInline):

    model = EntertainmentPhoto

class EntertainmentAdmin(CustomModelAdmin):

    filter_horizontal = ["types"]
    list_display = Entertainment.list_display
    list_filter = ["provider", "types", ]
    inlines = [EntertainmentPhotoInline]

admin.site.register(Entertainment, EntertainmentAdmin)

写真なしでエンターテイメント オブジェクトを追加し、編集時に写真を追加すると、すべてが正常に機能します。しかし、エンターテイメントを追加するときに写真を追加しようとすると、次の例外が発生します。

> Environment:
> 
> 
> Request Method: POST Request URL:
> http://mydomain.com/admin/entertainment/entertainment/add/
> 
> Django Version: 1.5b2 Python Version: 2.7.3 Installed Applications:
> ['south',  'gunicorn',  'django_extensions', 
> 'django.contrib.databrowse',  'django.contrib.contenttypes', 
> 'django.contrib.sessions',  'django.contrib.messages', 
> 'django.contrib.staticfiles',  'django.contrib.admin', 
> 'authentication',  'framework',  'framework.menu',  'services', 
> 'maps',  'services.entertainment',  'services.otherservices']
> Installed Middleware: ('django.middleware.common.CommonMiddleware', 
> 'django.contrib.sessions.middleware.SessionMiddleware', 
> 'django.middleware.csrf.CsrfViewMiddleware', 
> 'django.contrib.auth.middleware.AuthenticationMiddleware', 
> 'django.contrib.messages.middleware.MessageMiddleware', 
> 'django.middleware.clickjacking.XFrameOptionsMiddleware')
> 
> 
> Traceback: File
> "/Users/aemdy/virtualenvs/django1.5/lib/python2.7/site-packages/django/core/handlers/base.py"
> in get_response
>   116.                         response = callback(request, *callback_args, **callback_kwargs) File "/Users/aemdy/virtualenvs/django1.5/lib/python2.7/site-packages/django/contrib/admin/options.py"
> in wrapper
>   370.                 return self.admin_site.admin_view(view)(*args, **kwargs) File "/Users/aemdy/virtualenvs/django1.5/lib/python2.7/site-packages/django/utils/decorators.py"
> in _wrapped_view
>   91.                     response = view_func(request, *args, **kwargs) File "/Users/aemdy/virtualenvs/django1.5/lib/python2.7/site-packages/django/views/decorators/cache.py"
> in _wrapped_view_func
>   89.         response = view_func(request, *args, **kwargs) File "/Users/aemdy/virtualenvs/django1.5/lib/python2.7/site-packages/django/contrib/admin/sites.py"
> in inner
>   202.             return view(request, *args, **kwargs) File "/Users/aemdy/virtualenvs/django1.5/lib/python2.7/site-packages/django/utils/decorators.py"
> in _wrapper
>   25.             return bound_func(*args, **kwargs) File "/Users/aemdy/virtualenvs/django1.5/lib/python2.7/site-packages/django/utils/decorators.py"
> in _wrapped_view
>   91.                     response = view_func(request, *args, **kwargs) File "/Users/aemdy/virtualenvs/django1.5/lib/python2.7/site-packages/django/utils/decorators.py"
> in bound_func
>   21.                 return func(self, *args2, **kwargs2) File "/Users/aemdy/virtualenvs/django1.5/lib/python2.7/site-packages/django/db/transaction.py"
> in inner
>   208.                 return func(*args, **kwargs) File "/Users/aemdy/virtualenvs/django1.5/lib/python2.7/site-packages/django/contrib/admin/options.py"
> in add_view
>   1045.                 self.save_related(request, form, formsets, False) File
> "/Users/aemdy/virtualenvs/django1.5/lib/python2.7/site-packages/django/contrib/admin/options.py"
> in save_related
>   762.             self.save_formset(request, form, formset, change=change) File
> "/Users/aemdy/virtualenvs/django1.5/lib/python2.7/site-packages/django/contrib/admin/options.py"
> in save_formset
>   750.         formset.save() File "/Users/aemdy/virtualenvs/django1.5/lib/python2.7/site-packages/django/forms/models.py"
> in save
>   494.         return self.save_existing_objects(commit) + self.save_new_objects(commit) File
> "/Users/aemdy/virtualenvs/django1.5/lib/python2.7/site-packages/django/forms/models.py"
> in save_new_objects
>   628.             self.new_objects.append(self.save_new(form, commit=commit)) File
> "/Users/aemdy/virtualenvs/django1.5/lib/python2.7/site-packages/django/forms/models.py"
> in save_new
>   728.         pk_value = getattr(self.instance, self.fk.rel.field_name) File
> "/Users/aemdy/virtualenvs/django1.5/lib/python2.7/site-packages/django/db/models/fields/related.py"
> in __get__
>   389.             raise self.field.rel.to.DoesNotExist
> 
> Exception Type: DoesNotExist at
> /admin/entertainment/entertainment/add/ Exception Value: