old_contents: from django.conf.urls import url
  
  from . import views
  
  app_name = 'listings'
  
  urlpatterns = [
      url(r'^$', views.index, name='index'),
      url(r'^(?P<listing_id>[0-9]+)/$', views.detail, name='detail'),
  ]
  
new_contents: from django.conf.urls import url
  
  from . import views
  
  app_name = 'listings'
  
  urlpatterns = [
      url(r'^$', views.index, name='index'),
      url(r'^(?P<listing_id>[0-9]+)/$', views.detail, name='detail'),
      url(r'^newListing$', views.newListing, name='newListing'),
  ]
  
subject: Update newListing to urls.py