Django admin 中抛出 'WSGIRequest' object has no attribute 'user'的错误

这是Django版本的问题，1.9之前，中间件的key为MIDDLEWARE_CLASSES, 1.9之后，为MIDDLEWARE。所以在开发环境和其他环境的版本不一致时，要特别小心，会有坑。

将settings里的MIDDLEWARE_CLASSES默认配置顺序改成如下

MIDDLEWARE_CLASSES = [
    'django.middleware.security.SecurityMiddleware',
    'django.middleware.common.CommonMiddleware',
    'django.contrib.sessions.middleware.SessionMiddleware',
    'django.middleware.csrf.CsrfViewMiddleware',
    'django.contrib.auth.middleware.SessionAuthenticationMiddleware',
    'django.contrib.auth.middleware.AuthenticationMiddleware',
    'django.contrib.messages.middleware.MessageMiddleware',
    'django.middleware.clickjacking.XFrameOptionsMiddleware',
]