def post(self, request, *args, **kwargs):
    form_class = self.get_form_class()
form = self.get_form(form_class)
if form.is_valid():
    return self.form_valid(form)
else:
    return self.form_invalid(form, **kwargs)

def form_invalid(self, form, **kwargs):
    context = self.get_context_data(**kwargs)
context['form'] = form
return self.render_to_response(context)
Обновление данных контекста в методе FormView form_valid?