如何获取纯文本Django错误页面

我想写一个中间件，因为否则该异常在500.html中不可用

http://docs.djangoproject.com/en/dev/topics/http/middleware/#process-
exception

class ProcessExceptionMiddleware(object):    def process_exception(self, request, exception):        t = Template("500 Error: {{ exception }}")        response_html = t.render(Context({'exception' : exception }))        response = http.HttpResponse(response_html)        response.status_pre = 500        return response