问Django 1.6消息未显示

EN

MIDDLEWARE_CLASSES = (
    'django.middleware.common.CommonMiddleware',
    'django.contrib.sessions.middleware.SessionMiddleware',
    'django.middleware.csrf.CsrfViewMiddleware',
    'django.contrib.auth.middleware.AuthenticationMiddleware',
    'django.contrib.messages.middleware.MessageMiddleware',
    # Uncomment the next line for simple clickjacking protection:
    'django.middleware.clickjacking.XFrameOptionsMiddleware',
)

INSTALLED_APPS = (
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.sites',
    'django.contrib.messages',

from django.contrib import messages

def add_news(request):
    if request.method == 'POST':
        form = NewsForm(request.POST)
        if form.is_valid():
            form.save()
            messages.info(request, "News was added") 
            return HttpResponseRedirect('/')

    if request.method == 'GET':
        form = NewsForm()
        args = {}
        args.update(csrf(request))
        args['form'] = form
        return render_to_response('news/add_news.html', args)

  {% block messages %}
            {% if messages %}
            <ul class="messages">   
            {% for message in messages %}
               <li{% if message.tags %} class="{{ message.tags }}"{% endif %}>{{ message }}</li>
             {% endfor %}
             </ul>
        {% endif %}
  {% endblock messages %}