The view blog.views.post_detail didn't return an HttpResponse object. It returned None instead

Не получается зайти, после добавления комментариев.

views.py

from django.shortcuts import render, get_object_or_404, redirect
from django.views.generic import ListView
from .models import Post, Comment
from .forms import CommentForm


class PostListView(ListView):
    queryset = Post.published.all()
    context_object_name = 'posts'
    paginate_by = 3
    template_name = 'blog/post/list.html'


def post_detail(request, year, month, day, post):
    post = get_object_or_404(Post, slug=post, status='published',
                             publish__year=year, publish__month=month,
                             publish__day=day)
    # comments
    comments = post.comments.filter(active=True)
    new_comment = None
    if request.method == 'POST':
        # user send comment
        comment_form = CommentForm(data=request.POST)
        if comment_form.is_valid():
            new_comment = comment_form.save(commit=False)
            new_comment.post = post
            new_comment.save()
        else:
            comment_form = CommentForm()

    return render(request, 'blog/post/detail.html', {'post': post,
                                                     'comments': comments,
                                                     'new_comment': new_comment,
                                                     'comment_form': comment_form})

detail.html

 {% with comments.count as total_comments %}
    <h2>{{ total comments }} comment {{ total comments|pluralize }}</h2>
    {% endwith %}
    {% for comment in comments %}
        <div class="comment">
            <p class="info">
                Comment {{ forloop.counter }} by {{ comment.name }}
                {{ comment created }}
            </p>
            {{ comment.body|linebreaks }}
        </div>
    {% empty %}
        <p>There no comments yet.</p>
    {% endfor %}
    </div>
{% endblock %}