view newsletter.views.control新闻稿编辑未返回HttpResponse对象。但没有返回

这是我的url.py:

from django.urls import path
from newsletter.views import control_newsletter, control_newsletter_list, control_newsletter_detail, control_newsletter_edit

urlpatterns = [
    path('newsletter/', control_newsletter, name='control_newsletter'),
    path('newsletter_list/', control_newsletter_list, name='control_newsletter_list'),
    path('newsletter_detail/<int:pk>/', control_newsletter_detail, name='control_newsletter_detail'),
    path('newsletter_edit/<int:pk>/', control_newsletter_edit, name='control_newsletter_edit'),]

这是我的观点.py:

def control_newsletter_edit(request, pk):
    newsletter = get_object_or_404(Newsletter, pk=pk)
    if request.method == 'POST':

        form = NewsletterCreationForm(request.POST, instance=Newsletter)

        if form.is_valid():
            newsletter = form.save()

            if newsletter.status == 'Published':
                subject = newsletter.subject
                body = newsletter.body
                from_email = global_settings.EMAIL_HOST_USER
                for email in newsletter.email.all():
                    send_mail(subject=subject, from_email=from_email, recipient_list=[email], message=body,
                              fail_silently=True)
                messages.success(request, 'Your Changes Write Successfully.',
                                 'alert alert-success alert-dismissible')
            else:
                messages.warning(request, 'SomeThing Went Wrong..',
                                 'alert alert-warning alert-dismissible')
            return redirect('control_newsletter_detail', pk=newsletter.pk)

        else:
            form = NewsletterCreationForm(instance=newsletter)

            context = {
                'form': form,
            }

            return render(request, 'control_panel/control_newsletter.html', context)

当我试图接近 newsletter_edit/1/ 从这里开始,在我的teplate代码中:

<div class="col-sm-8">
            <div class="col-sm-2">
                <a href="{% url 'control_newsletter_edit' pk=newsletter.pk %}">
                    <button class="btn-success">Edit</button>
                </a>
            </div>

我面对这个错误:

ValueError at /panel/newsletter_edit/1/
The view newsletter.views.control_newsletter_edit didn't return an HttpResponse object. It returned None instead.

我一遍又一遍地检查我的url.py和views.py,但我无法找出我的问题所在。 有人知道我为什么要面对这个错误吗? 另外,我很抱歉在我的问题上写了错误。 如果你需要我的全部观点,请告诉我。