django安装自己的中间件的问题

我在站点根目录里建立了contrib/auth/，里面有一个middleware.py文件，包含一个AuthenticationMiddleware类。
在settings.py的MIDDLEWARE_CLASSES里改成：
MIDDLEWARE_CLASSES = (
  'django.contrib.sessions.middleware.SessionMiddleware',
  'django.contrib.auth.middleware.AuthenticationMiddleware',
  'site1.contrib.auth.middleware.AuthenticationMiddleware',
)

运行后发生错误：ImproperlyConfigured: Error importing middleware site1.contrib.auth.middleware: "No module named contrib.auth.middleware"
但是把middleware.py直接放在站点根目录，MIDDLEWARE_CLASSES改成：
MIDDLEWARE_CLASSES = (
  'django.contrib.sessions.middleware.SessionMiddleware',
  'django.contrib.auth.middleware.AuthenticationMiddleware',
  'site1.middleware.AuthenticationMiddleware',
)

谢谢大家！

试试你的路径contrib/和contrib/auth/下都加个空的__init__.py