old_contents: """
  Test settings for ``polymorphic_auth`` app.
  """
  
  AUTH_USER_MODEL = 'polymorphic_auth.User'
  POLYMORPHIC_AUTH = {
      'DEFAULT_CHILD_MODEL': 'polymorphic_auth_email.EmailUser',
  }
  
  DATABASES = {
      'default': {
          'ATOMIC_REQUESTS': True,
          'ENGINE': 'django.db.backends.postgresql_psycopg2',
          'NAME': 'polymorphic_auth',
      }
  }
  
  DEBUG = True
  EMAIL_BACKEND = 'django.core.mail.backends.console.EmailBackend'
  
  INSTALLED_APPS = (
      'django.contrib.admin',
      'django.contrib.auth',
      'django.contrib.contenttypes',
      'django.contrib.sessions',
      'django.contrib.staticfiles',
      'django_nose',
      'polymorphic_auth',
      'polymorphic_auth.tests',
      'polymorphic_auth.usertypes.email',
  )
  
  MIDDLEWARE_CLASSES = (
      'django.contrib.sessions.middleware.SessionMiddleware',
      'django.contrib.auth.middleware.AuthenticationMiddleware',
  )
  
  ROOT_URLCONF = 'polymorphic_auth.tests.urls'
  SECRET_KEY = 'secret-key'
  STATIC_URL = '/static/'
  TEST_RUNNER = 'django_nose.NoseTestSuiteRunner'
  
new_contents: """
  Test settings for ``polymorphic_auth`` app.
  """
  
  AUTH_USER_MODEL = 'polymorphic_auth.User'
  POLYMORPHIC_AUTH = {
      'DEFAULT_CHILD_MODEL': 'polymorphic_auth_email.EmailUser',
  }
  
  DATABASES = {
      'default': {
          'ATOMIC_REQUESTS': True,
          'ENGINE': 'django.db.backends.postgresql_psycopg2',
          'NAME': 'polymorphic_auth',
      }
  }
  
  DEBUG = True
  EMAIL_BACKEND = 'django.core.mail.backends.console.EmailBackend'
  
  INSTALLED_APPS = (
      'django.contrib.admin',
      'django.contrib.auth',
      'django.contrib.contenttypes',
      'django.contrib.sessions',
      'django.contrib.staticfiles',
      'django_nose',
      'polymorphic',
      'polymorphic_auth',
      'polymorphic_auth.tests',
      'polymorphic_auth.usertypes.email',
  )
  
  MIDDLEWARE_CLASSES = (
      'django.contrib.sessions.middleware.SessionMiddleware',
      'django.contrib.auth.middleware.AuthenticationMiddleware',
      'django.contrib.messages.middleware.MessageMiddleware',
  )
  
  ROOT_URLCONF = 'polymorphic_auth.tests.urls'
  SECRET_KEY = 'secret-key'
  STATIC_URL = '/static/'
  TEST_RUNNER = 'django_nose.NoseTestSuiteRunner'
  
subject: Add `polymorphic` to `INSTALLED_APPS`, and also `MessageMiddlware` (because Django wants it).