Upgrading from 3.2.2 to 3.2.3 throw TypeError: 'NoneType' object is not iterable

The following requirements work fine with tests suite

django-filter==0.11.0
django-model-utils==2.3.1
Django==1.8.4
djangorestframework==3.2.2
drf-extensions==0.2.7

Error

Upgrading to djangorestframework 3.2.3, tests throw this :

Traceback (most recent call last):
  File "projects/xyz/core/tests/test_accounts.py", line 60, in test_can_list_accounts
    response = self.client.get('/api/accounts/', format='json')
  File ".virtualenvs/xyz/lib/python3.4/site-packages/rest_framework/test.py", line 162, in get
    response = super(APIClient, self).get(path, data=data, **extra)
  File ".virtualenvs/xyz/lib/python3.4/site-packages/rest_framework/test.py", line 88, in get
    return self.generic('GET', path, **r)
  File ".virtualenvs/xyz/lib/python3.4/site-packages/django/test/client.py", line 379, in generic
    return self.request(**r)
  File ".virtualenvs/xyz/lib/python3.4/site-packages/rest_framework/test.py", line 159, in request
    return super(APIClient, self).request(**kwargs)
  File ".virtualenvs/xyz/lib/python3.4/site-packages/rest_framework/test.py", line 111, in request
    request = super(APIRequestFactory, self).request(**kwargs)
  File ".virtualenvs/xyz/lib/python3.4/site-packages/django/test/client.py", line 466, in request
    six.reraise(*exc_info)
  File ".virtualenvs/xyz/lib/python3.4/site-packages/django/utils/six.py", line 659, in reraise
    raise value
  File ".virtualenvs/xyz/lib/python3.4/site-packages/django/core/handlers/base.py", line 132, in get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File ".virtualenvs/xyz/lib/python3.4/site-packages/django/views/decorators/csrf.py", line 58, in wrapped_view
    return view_func(*args, **kwargs)
  File ".virtualenvs/xyz/lib/python3.4/site-packages/rest_framework/viewsets.py", line 87, in view
    return self.dispatch(request, *args, **kwargs)
  File ".virtualenvs/xyz/lib/python3.4/site-packages/rest_framework/views.py", line 466, in dispatch
    response = self.handle_exception(exc)
  File ".virtualenvs/xyz/lib/python3.4/site-packages/rest_framework/views.py", line 463, in dispatch
    response = handler(request, *args, **kwargs)
  File ".virtualenvs/xyz/lib/python3.4/site-packages/rest_framework/mixins.py", line 40, in list
    queryset = self.filter_queryset(self.get_queryset())
  File ".virtualenvs/xyz/lib/python3.4/site-packages/rest_framework/generics.py", line 151, in filter_queryset
    queryset = backend().filter_queryset(self.request, queryset, self)
  File ".virtualenvs/xyz/lib/python3.4/site-packages/rest_framework/filters.py", line 107, in filter_queryset
    for search_field in search_fields
TypeError: 'NoneType' object is not iterable

Test

    def test_can_list_accounts(self):
        self.client.force_authenticate(user=self.cust_admin)
        response = self.client.get('/api/accounts/', format='json')
        self.assertEqual(response.status_code, status.HTTP_200_OK)
        self.assertEqual(response.data['count'], 1)

Views

class AccountViewSet(viewsets.ModelViewSet):
    queryset = Account.objects.all()
    serializer_class = AccountSerializer

    def get_queryset(self):
        customer = self.request.user.customer
        if customer:
            return self.queryset.filter(customer=customer)
        return self.queryset

Serializer

class AccountSerializer(serializers.ModelSerializer):
    group = serializers.SlugRelatedField(slug_field='name', queryset=Group.objects.all(), required=False, allow_null=True)
    new_password = serializers.CharField(max_length=128, required=False, allow_null=True, write_only=True)

    class Meta:
        model = Account
        fields = ('id', 'url', 'username', 'first_name', 'last_name', 'email', 'group', 'customer', 'is_superuser', 'is_active',
                  'date_joined', 'last_login', 'new_password', 'default_warehouse', 'current_warehouse', 'default_customer', 'current_customer')
        read_only_fields = ('date_joined', 'last_login')
        write_only_fields = ('new_password',)

    def update(self, instance, validated_data):
        instance = super(AccountSerializer, self).update(instance, validated_data)
        pwd = validated_data.get('new_password')
        if pwd:
            instance.set_password(pwd)
        instance.save()
        return instance

    @transaction.atomic
    def create(self, validated_data):
        pwd = validated_data.pop('new_password', None)
        group = validated_data.pop('group', None)
        account =  Account.objects.create(**validated_data)
        if pwd:
            account.set_password(pwd)
            account.save()
        if group:
            account.group = group
            account.save()
        return account

Questions

The 3.2.3 release only speak about Added regex style to SearchFilter. (#3316).

Any suggestion what's the matter here?

encode / django-rest-framework

Upgrading from 3.2.2 to 3.2.3 throw TypeError: 'NoneType' object is not iterable #3379

Error

Test

Views

Serializer

Questions