如何找不到nginx try_files日志文件？

server {
    server_name foo.com;

    listen 80;

    root '/var/www';

    location /divergent {
        try_files 'bar' =400;
    }
}

在这个例子中,我想得到一条消息,如：

2015/03/27 17:53:49 [error] 25248#0: *1 open() '/var/www/bar' failed (2: No such file or directory),client: 37.187.147.109,server: foo.com,request: "GET /bar HTTP/1.1",host: "foo.com"

我想得到上述消息;我有时会得到它,有时候我没有.我不明白是什么让消息传播.

HTTP块配置为记录所有消息：

http {
    error_log /var/log/nginx/error.log debug;

    # ...
}