ExerciseCreateView.py

class ExerciseCreateView(OnlySelectedUsersOrSuperuserMixin, CreateView):
    model = models.Exercise
    fields = ['name', 'text']

    def dispatch(self, request, *args, **kwargs):
        self._workshop = models.Workshop.objects.get(pk=self.kwargs['workshop__pk'])
        self.selectedUsers = (self._workshop.host,)
        return super().dispatch(request, *args, **kwargs)

    def get_context_data(self, **kwargs):
        context = super().get_context_data(**kwargs)
        context['workshop'] = self._workshop
        return context

    def form_valid(self, form):
        obj = form.save(commit=False)
        obj.workshop = models.Workshop.objects.get(
            pk=self.kwargs['workshop__pk'])
        obj.save()
        return http.HttpResponseRedirect(reverse_lazy('exercise', args=(obj.pk,)))