old_contents: from django.conf.urls import url
  from discussion import views
  
  urlpatterns = [
      url(r'^comments/(?P<pk>[0-9]+)/$',
          views.CommentDetail.as_view(),
          name='comment-detail'),
      url(r'^discussions/$',
          views.DiscussionList.as_view(),
          name='discussion-list'),
      url(r'^discussions/(?P<pk>[0-9]+)/$',
          views.DiscussionDetail.as_view(),
          name='discussion-detail'),
      url(r'^discussions/(?P<pk>[0-9]+)/comments/$',
          views.DiscussionComments.as_view(),
          name='discussion-comments'),
  ]
  
new_contents: from django.conf.urls import url
  from discussion import views
  
  urlpatterns = [
      url(r'^comments/(?P<pk>[0-9]+)/$',
          views.CommentDetail.as_view(),
          name='comment-detail'),
      url(r'^$',
          views.DiscussionList.as_view(),
          name='discussion-list'),
      url(r'^(?P<pk>[0-9]+)/$',
          views.DiscussionDetail.as_view(),
          name='discussion-detail'),
      url(r'^(?P<pk>[0-9]+)/comments/$',
          views.DiscussionComments.as_view(),
          name='discussion-comments'),
  ]
  
subject: Change long discussion urls.