强制转换为Unicode：需要字符串或缓冲区，在django模板中找到instancemethod

Question

我有一个版本为1.2.4的django应用程序并更新为1.6.5，我已经将很多网址结构从{% url name %}更改为{% url 'name' %}但是在一个地方它导致了我以下

回溯

File "/home/user/.virtualenvs/proj/local/lib/python2.7/site-packages/django/core/urlresolvers.py" in _populate
  278.                     lookup_str = callback.__module__ + "." + callback.__name__

Exception Type: TypeError at /store/
Exception Value: coercing to Unicode: need string or buffer, instancemethod found

导致错误的模板代码

<ul id="product-tabs">
    <li class="passive"><span><a href={% url "webstore_new" passive_year %}>{{ passive_year }}</a></span></li>
    <li><span><a href={% url "webstore_new" active_year %}>{{ active_year }}</a></span></li>
</ul>

那么上面模板代码中的url标记有什么问题？

修改

views.py

def products(request, year=None):
  current_site = Site.objects.get_current()
  present_year = datetime.datetime.now().year
  if Products.objects.filter(year__contains = present_year+1):
    active_year = present_year + 1
    passive_year = present_year
  else:
    active_year = present_year
    passive_year = present_year - 1

    products = Products.objects.filter(Q(site=current_site, year=year))
  .....
  ......
  .......      
  variables = {
    'obj': products,
    'active_year': active_year,
    'passive_year': passive_year,
  }

  response = RequestContext(request, variables)
  return render_to_response('new/store/webstore.html', response)