Django и фильтр через Q = Error «too many values to unpack»

    class SearchResultView(ListView, ProcessFormView):
        ...
    
        def get(self, request, *args, **kwargs):
            return super(SearchResultView, self).get(request, *args, **kwargs)
    
        def post(self, request, *args, **kwargs):
          
            self.search_form = SearchForm(self.request.POST or None)

            if self.search_form.is_valid():
                search_term = u"%s" % self.search_form.cleaned_data['search_term']
                g_list = None

                if search_term:

                    try:
                        g_list = Gallery.objects.filter(
                            Q(article__icontains=search_term) |
                            Q(category__title__icontains=search_term) |
                            Q(tags__tag__icontains=search_term)
                         )
                    except ValueError as e:
                        print("Error! ", e.message)
                    
                return g_list

            else:
                return super(SearchResultView, self).post(request, *args, **kwargs)
    
        ...

    too many values to unpack
    
    Request Method: 	POST
    Request URL: 	http://127.0.0.1:8000/gallery/search_result/
    Django Version: 	1.7.5
    Exception Type: 	ValueError
    Exception Value: 	
    
    too many values to unpack
    
    Exception Location: 	/.../lib/python2.7/site-packages/django/db/models/sql/query.py in build_filter, line 1179
    Python Executable: 	/.../bin/python
    Python Version: 	2.7.9

g_list = Gallery.objects.filter(
    Q(article__icontains=search_term) |
    Q(category__title__icontains=search_term) |
    Q(tags__tag__icontains=search_term)
)