if self.cleaned_data['period_end_type'] == 'a specific past date' and not self.cleaned_data['period_ends']:

            raise ValidationError('This field is required')

            ['denver@sfconservancy.org', 'bsturmfels@sfconservancy.org'],

        )

        return super().form_valid(form)

    def get_success_url(self, *args, **kwargs):

        return reverse_lazy('assignment-thanks', kwargs={'pk': str(self.object.uuid)})