Return string if QuerySet is empty
<p>In the following code, if the queryset is empty, I would like to return a string where the <code>results</code> field appears on the JSON response.</p>

<p>As is, I get an error saying <code>object of type 'Response' has no len()</code>. Does anyone know how to return a string in this instance?</p>

<p>Thank you!</p>

<pre><code>class ProductListAPIView(CacheMixin, DefaultsMixin, FiltersMixin,
                         generics.ListAPIView):
    serializer_class = ProductSerializer
    search_fields = ('title', 'owner',)
    ordering_fields = ('created', 'modified', 'list_date_start',)

    def get_queryset(self):
        products = (Product.objects.select_related('owner')
                                   .prefetch_related('buyers'))
        for product in products:
            listuse_status_check.send(sender=product)
        queryset = products.filter(is_listed=True)
        if queryset:
            return queryset
        return RestResponse({'results': 'some string here.'})
</code></pre>