old_contents: from __future__ import absolute_import, unicode_literals
  
  
  DATABASES = {"default": {"ENGINE": "django.db.backends.sqlite3", "NAME": ":memory:"}}
  INSTALLED_APPS = (
      "django.contrib.auth",
      "django.contrib.admin",
      "django.contrib.contenttypes",
      "django.contrib.sessions",
      "django.contrib.sitemaps",
      "django.contrib.sites",
      "django.contrib.staticfiles",
      "testapp",
      "content_editor",
  )
  STATIC_URL = "/static/"
  SECRET_KEY = "tests"
  ROOT_URLCONF = "testapp.urls"
  ALLOWED_HOSTS = ["*"]
  MIDDLEWARE_CLASSES = (
      "django.middleware.common.CommonMiddleware",
      "django.contrib.sessions.middleware.SessionMiddleware",
      "django.middleware.csrf.CsrfViewMiddleware",
      "django.contrib.auth.middleware.AuthenticationMiddleware",
      "django.contrib.messages.middleware.MessageMiddleware",
      "django.middleware.locale.LocaleMiddleware",
      "django.contrib.auth.middleware.SessionAuthenticationMiddleware",
  )
  MIDDLEWARE = (
      "django.middleware.common.CommonMiddleware",
      "django.contrib.sessions.middleware.SessionMiddleware",
      "django.middleware.csrf.CsrfViewMiddleware",
      "django.contrib.auth.middleware.AuthenticationMiddleware",
      "django.contrib.messages.middleware.MessageMiddleware",
      "django.middleware.locale.LocaleMiddleware",
  )
  SILENCED_SYSTEM_CHECKS = ["1_10.W001"]
  USE_TZ = True
  LANGUAGES = (("en", "English"), ("de", "German"))
  TEMPLATES = [
      {
          "BACKEND": "django.template.backends.django.DjangoTemplates",
          "DIRS": [],
          "APP_DIRS": True,
          "OPTIONS": {
              "context_processors": [
                  "django.template.context_processors.debug",
                  "django.template.context_processors.request",
                  "django.contrib.auth.context_processors.auth",
                  "django.contrib.messages.context_processors.messages",
              ]
          },
      }
  ]
  
new_contents: from __future__ import absolute_import, unicode_literals
  
  
  DATABASES = {"default": {"ENGINE": "django.db.backends.sqlite3", "NAME": ":memory:"}}
  INSTALLED_APPS = (
      "django.contrib.auth",
      "django.contrib.admin",
      "django.contrib.contenttypes",
      "django.contrib.messages",
      "django.contrib.sessions",
      "django.contrib.sitemaps",
      "django.contrib.sites",
      "django.contrib.staticfiles",
      "testapp",
      "content_editor",
  )
  STATIC_URL = "/static/"
  SECRET_KEY = "tests"
  ROOT_URLCONF = "testapp.urls"
  ALLOWED_HOSTS = ["*"]
  MIDDLEWARE_CLASSES = (
      "django.middleware.common.CommonMiddleware",
      "django.contrib.sessions.middleware.SessionMiddleware",
      "django.middleware.csrf.CsrfViewMiddleware",
      "django.contrib.auth.middleware.AuthenticationMiddleware",
      "django.contrib.messages.middleware.MessageMiddleware",
      "django.middleware.locale.LocaleMiddleware",
      "django.contrib.auth.middleware.SessionAuthenticationMiddleware",
  )
  MIDDLEWARE = (
      "django.middleware.common.CommonMiddleware",
      "django.contrib.sessions.middleware.SessionMiddleware",
      "django.middleware.csrf.CsrfViewMiddleware",
      "django.contrib.auth.middleware.AuthenticationMiddleware",
      "django.contrib.messages.middleware.MessageMiddleware",
      "django.middleware.locale.LocaleMiddleware",
  )
  SILENCED_SYSTEM_CHECKS = ["1_10.W001"]
  USE_TZ = True
  LANGUAGES = (("en", "English"), ("de", "German"))
  TEMPLATES = [
      {
          "BACKEND": "django.template.backends.django.DjangoTemplates",
          "DIRS": [],
          "APP_DIRS": True,
          "OPTIONS": {
              "context_processors": [
                  "django.template.context_processors.debug",
                  "django.template.context_processors.request",
                  "django.contrib.auth.context_processors.auth",
                  "django.contrib.messages.context_processors.messages",
              ]
          },
      }
  ]
  
subject: Add django.contrib.messages to INSTALLED_APPS, Django 2.1's admin app requires it