创建Django权限，错误：ContentType匹配查询不存在

Question

我试图添加两个组，并授予它们对我的Django项目的权限。但我一直有个错误：

ContentType匹配查询不存在。

我在跑： Django 1.5.4公司 Python2.7.3 南0.8.2 PostreSQL 9.3版

这是我的代码：

import django
from django.contrib.auth.models import Group, Permission
from django.contrib.contenttypes.models import ContentType 

from .models import Flavor

def add_groups():
    # Create User Groups
    special_users = Group(name='Special Users')
    special_users.save()
    really_special_users = Group(name='Super Special Users')
    really_special_users.save()

def add_permissions():
    # Define a View permission for the 1st group, and a View/Modify permission for the 2nd group
    somemodel_ct = ContentType.objects.get(app_label='flavors', model='flavors_flavor')
    can_view = Permission(name='Can View', codename='can_view_something', content_type=somemodel_ct)
    can_view.save()
    can_modify = Permission(name='Can Modify', codename='can_modify_something', content_type=somemodel_ct)
    can_modify.save()

def give_perm_to_groups():
    # Associate these two permissions now with a Group
    special_users.permissions.add(can_view)
    really_special_users.permissions = [can_view, can_modify]

我可以运行add_groups（）很好。正在工作的是add_permissions（）。我相信这与Postgres中的fixtures有关，但不确定如何添加它们，或者这是否是真正的问题？

谢谢

以下是整个错误回溯：

>>> add_permissions()
Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "/Users/Yuki_Aaron/Documents/djcode/demoproject/flavors/groups.py", line 16, in add_permissions
    somemodel_ct = ContentType.objects.get(app_label='flavors', model='flavors_flavor')
  File "/Users/Yuki_Aaron/Documents/virtualenvs/django1.5/lib/python2.7/site-packages/django/db/models/manager.py", line 143, in get
    return self.get_query_set().get(*args, **kwargs)
  File "/Users/Yuki_Aaron/Documents/virtualenvs/django1.5/lib/python2.7/site-packages/django/db/models/query.py", line 404, in get
    self.model._meta.object_name)
DoesNotExist: ContentType matching query does not exist.