'type' object is not iterable when I use any decorators

Hello,

Here is a decorator that I am trying ot use to restrict access to the class to only super users: Can someone please point me to what could be wrong. If I take the decorator, I am able to get thro but it is not restricted to only super users.

@user_passes_test(lambda u: u.is_superuser)
class UserViewSet(viewsets.ModelViewSet):
    permission_classes = [permissions.TokenHasReadWriteScope]
    queryset = User.objects.all()
    serializer_class = UserSerializer
    model=User

When I use this, I get the error:

'type' object is not iterable

TypeError at /users/
'type' object is not iterable
Request Method:
GET
Request URL:
http://127.0.0.1:8000/users/
Django Version:
1.8
Exception Type:
TypeError
Exception Value:
'type' object is not iterable
Exception Location:
/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/rest_framework/views.py in get_permissions, line 252
Python Executable:
/Library/Frameworks/Python.framework/Versions/3.4/bin/python3.4
Python Version:
3.4.3
Python Path:
['/Users/PycharmProjects/screens',   '/Users/PycharmProjects/screens',   '/Library/Frameworks/Python.framework/Versions/3.4/lib/python34.zip',   '/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4',   '/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/plat-darwin',   '/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/lib-dynload',   '/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages']

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