old_contents: from settings import *
  INSTALLED_APPS.append('complex')
  INSTALLED_APPS.append('django.contrib.comments')
  
  ROOT_URLCONF = 'complex.urls'
  
new_contents: from settings import *
  
  INSTALLED_APPS += [
      'complex',
      'django.contrib.comments',
      'django.contrib.sites',
  ]
  
  ROOT_URLCONF = 'complex.urls'
  
subject: Add sites app, change how installed_apps are edited.