python - Wagtail 0.8.6 - admin - NoneType' object has no attribute 'allowed_subpage_types' -

i'm using wagtail 0.8.6 django 1.7.7, when try access specific page in admin:

http://127.0.0.1:8020/admin/pages/4/ 

i following error:

attributeerror @ /admin/pages/4/ 'nonetype' object has no attribute 'allowed_subpage_types' 

this traceback:

environment:   request method: request url: http://127.0.0.1:8020/admin/pages/4/  django version: 1.7.7 python version: 2.7.3 installed applications: ('django.contrib.auth',  'django.contrib.contenttypes',  'django.contrib.sessions',  'django.contrib.messages',  'django.contrib.staticfiles',  'raven.contrib.django.raven_compat',  'compressor',  'taggit',  'modelcluster',  'django.contrib.admin',  'preventconcurrentlogins',  'django_medusa',  'wagtail.wagtailcore',  'wagtail.wagtailadmin',  'wagtail.wagtaildocs',  'wagtail.wagtailsnippets',  'wagtail.wagtailusers',  'wagtail.wagtailimages',  'wagtail.wagtailembeds',  'wagtail.wagtailsearch',  'wagtail.wagtailredirects',  'wagtail.contrib.wagtailmedusa',  'myapp',  'django_extensions') 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',  'preventconcurrentlogins.middleware.preventconcurrentloginsmiddleware',  'wagtail.wagtailcore.middleware.sitemiddleware',  'wagtail.wagtailredirects.middleware.redirectmiddleware')   template error: in template /home/vagrant/venv/local/lib/python2.7/site-packages/wagtail/wagtailadmin/templates/wagtailadmin/pages/list.html, error @ line 265    'nonetype' object has no attribute 'allowed_subpage_types'    255 :                         {% if allow_navigation %}      256 :                             {% if moving %}      257 :                                 {% if page.can_descend %}      258 :                                     <a href="{% url 'wagtailadmin_pages_move_choose_destination' page_to_move.id page.id %}" class="icon text-replace icon-arrow-right navigate-pages" title="{% blocktrans title=page.title %}explorer subpages of '{{ title }}'{% endblocktrans %}">{% trans 'explore' %}</a>      259 :                                 {% endif %}      260 :                             {% elif choosing %}      261 :                                 {% if page.can_descend %}      262 :                                     <a href="{% url 'wagtailadmin_choose_page_child' page.id %}?{{ querystring }}" class="icon text-replace icon-arrow-right navigate-pages" title="{% blocktrans title=page.title %}explorer subpages of '{{ title }}'{% endblocktrans %}">{% trans 'explore' %}</a>      263 :                                 {% endif %}      264 :                             {% else %}      265 :                                  {% if page.is_navigable %}       266 :                                     <a href="{% url 'wagtailadmin_explore' page.id %}" class="icon text-replace icon-arrow-right" title="{% blocktrans title=page.title %}explore child pages of '{{ title }}'{% endblocktrans %}">{% trans "explore" %}</a>      267 :                                 {% elif page_perms.can_add_subpage %}      268 :                                     <a href="{% url 'wagtailadmin_pages_add_subpage' page.id %}" class="icon text-replace icon-plus-inverse" title="{% blocktrans title=page.title %}add child page '{{ title }}'{% endblocktrans %}">{% trans 'add subpage' %}</a>      269 :                                 {% endif %}      270 :                             {% endif %}      271 :                         {% endif %}      272 :                      </td>      273 :                 </tr>      274 :             {% endfor %}      275 :         {% else %}   traceback: file "/home/vagrant/venv/local/lib/python2.7/site-packages/django/core/handlers/base.py" in get_response   111.                     response = wrapped_callback(request, *callback_args, **callback_kwargs) file "/home/vagrant/venv/local/lib/python2.7/site-packages/django/contrib/auth/decorators.py" in _wrapped_view   21.                 return view_func(request, *args, **kwargs) file "/home/vagrant/venv/local/lib/python2.7/site-packages/wagtail/wagtailadmin/views/pages.py" in index   65.         'pages': pages, file "/home/vagrant/venv/local/lib/python2.7/site-packages/django/shortcuts.py" in render   50.     return httpresponse(loader.render_to_string(*args, **kwargs), file "/home/vagrant/venv/local/lib/python2.7/site-packages/django/template/loader.py" in render_to_string   178.         return t.render(context_instance) file "/home/vagrant/venv/local/lib/python2.7/site-packages/django/template/base.py" in render   148.             return self._render(context) file "/home/vagrant/venv/local/lib/python2.7/site-packages/django/template/base.py" in _render   142.         return self.nodelist.render(context) file "/home/vagrant/venv/local/lib/python2.7/site-packages/django/template/base.py" in render   844.                 bit = self.render_node(node, context) file "/home/vagrant/venv/local/lib/python2.7/site-packages/django/template/debug.py" in render_node   80.             return node.render(context) file "/home/vagrant/venv/local/lib/python2.7/site-packages/django/template/loader_tags.py" in render   126.         return compiled_parent._render(context) file "/home/vagrant/venv/local/lib/python2.7/site-packages/django/template/base.py" in _render   142.         return self.nodelist.render(context) file "/home/vagrant/venv/local/lib/python2.7/site-packages/django/template/base.py" in render   844.                 bit = self.render_node(node, context) file "/home/vagrant/venv/local/lib/python2.7/site-packages/django/template/debug.py" in render_node   80.             return node.render(context) file "/home/vagrant/venv/local/lib/python2.7/site-packages/django/template/loader_tags.py" in render   126.         return compiled_parent._render(context) file "/home/vagrant/venv/local/lib/python2.7/site-packages/django/template/base.py" in _render   142.         return self.nodelist.render(context) file "/home/vagrant/venv/local/lib/python2.7/site-packages/django/template/base.py" in render   844.                 bit = self.render_node(node, context) file "/home/vagrant/venv/local/lib/python2.7/site-packages/django/template/debug.py" in render_node   80.             return node.render(context) file "/home/vagrant/venv/local/lib/python2.7/site-packages/django/template/loader_tags.py" in render   126.         return compiled_parent._render(context) file "/home/vagrant/venv/local/lib/python2.7/site-packages/django/template/base.py" in _render   142.         return self.nodelist.render(context) file "/home/vagrant/venv/local/lib/python2.7/site-packages/django/template/base.py" in render   844.                 bit = self.render_node(node, context) file "/home/vagrant/venv/local/lib/python2.7/site-packages/django/template/debug.py" in render_node   80.             return node.render(context) file "/home/vagrant/venv/local/lib/python2.7/site-packages/django/template/loader_tags.py" in render   65.                 result = block.nodelist.render(context) file "/home/vagrant/venv/local/lib/python2.7/site-packages/django/template/base.py" in render   844.                 bit = self.render_node(node, context) file "/home/vagrant/venv/local/lib/python2.7/site-packages/django/template/debug.py" in render_node   80.             return node.render(context) file "/home/vagrant/venv/local/lib/python2.7/site-packages/django/template/loader_tags.py" in render   65.                 result = block.nodelist.render(context) file "/home/vagrant/venv/local/lib/python2.7/site-packages/django/template/base.py" in render   844.                 bit = self.render_node(node, context) file "/home/vagrant/venv/local/lib/python2.7/site-packages/django/template/debug.py" in render_node   80.             return node.render(context) file "/home/vagrant/venv/local/lib/python2.7/site-packages/django/template/loader_tags.py" in render   150.                 return template.render(context) file "/home/vagrant/venv/local/lib/python2.7/site-packages/django/template/base.py" in render   148.             return self._render(context) file "/home/vagrant/venv/local/lib/python2.7/site-packages/django/template/base.py" in _render   142.         return self.nodelist.render(context) file "/home/vagrant/venv/local/lib/python2.7/site-packages/django/template/base.py" in render   844.                 bit = self.render_node(node, context) file "/home/vagrant/venv/local/lib/python2.7/site-packages/django/template/debug.py" in render_node   80.             return node.render(context) file "/home/vagrant/venv/local/lib/python2.7/site-packages/django/template/defaulttags.py" in render   312.                 return nodelist.render(context) file "/home/vagrant/venv/local/lib/python2.7/site-packages/django/template/base.py" in render   844.                 bit = self.render_node(node, context) file "/home/vagrant/venv/local/lib/python2.7/site-packages/django/template/debug.py" in render_node   80.             return node.render(context) file "/home/vagrant/venv/local/lib/python2.7/site-packages/django/template/defaulttags.py" in render   201.                             nodelist.append(node.render(context)) file "/home/vagrant/venv/local/lib/python2.7/site-packages/django/template/defaulttags.py" in render   312.                 return nodelist.render(context) file "/home/vagrant/venv/local/lib/python2.7/site-packages/django/template/base.py" in render   844.                 bit = self.render_node(node, context) file "/home/vagrant/venv/local/lib/python2.7/site-packages/django/template/debug.py" in render_node   80.             return node.render(context) file "/home/vagrant/venv/local/lib/python2.7/site-packages/django/template/defaulttags.py" in render   312.                 return nodelist.render(context) file "/home/vagrant/venv/local/lib/python2.7/site-packages/django/template/base.py" in render   844.                 bit = self.render_node(node, context) file "/home/vagrant/venv/local/lib/python2.7/site-packages/django/template/debug.py" in render_node   80.             return node.render(context) file "/home/vagrant/venv/local/lib/python2.7/site-packages/django/template/defaulttags.py" in render   305.                     match = condition.eval(context) file "/home/vagrant/venv/local/lib/python2.7/site-packages/django/template/defaulttags.py" in eval   898.         return self.value.resolve(context, ignore_failures=true) file "/home/vagrant/venv/local/lib/python2.7/site-packages/django/template/base.py" in resolve   596.                 obj = self.var.resolve(context) file "/home/vagrant/venv/local/lib/python2.7/site-packages/django/template/base.py" in resolve   734.             value = self._resolve_lookup(context) file "/home/vagrant/venv/local/lib/python2.7/site-packages/django/template/base.py" in _resolve_lookup   788.                             current = current() file "/home/vagrant/venv/local/lib/python2.7/site-packages/wagtail/wagtailcore/models.py" in can_add_subpage   1269.         if not self.page.specific_class.allowed_subpage_types():  # page model has empty subpage_types list, no subpages allowed  exception type: attributeerror @ /admin/pages/4/ exception value: 'nonetype' object has no attribute 'allowed_subpage_types' 

before upgrade, wagtail 0.5 , django 1.6.5 working. idea of can cause that?

i hit bug today well.

i found line of code in wagtailcore models.py file , added print statement narrow down page causing issue.

def can_add_subpage(self):    print self 

from there checked wagtailcore_page table in database , found specific page. in case pointing content type model no longer being used , updated database accordingly.

you can test out in shell.

from wagtail.wagtailcore.models import page pages = page.objects.all() p in pages:     if not p.specific_class:         print p 

i've seen happen in cms's, create page of type , and delete/rename model old data stays in page tree. try make sure have deleted content types in cms first, before removing code.

hopefully point in right direction. wagtail on.