如何解决“禁止Nginx”错误？

Question

我将在服务器上部署Nginx开发的Tornado Web应用程序，但是会出现此错误：

*4 directory index of "/usr/share/nginx/html/dir/" is forbidden, client:xxx.xxx.x.xxx, server: host.name, request: "GET / HTTP/1.1", host: "host.name"

这是Nginx的设置文件：

server {
    listen 443 ssl;
    server_name host.name;

    ssl_certificate     /etc/letsencrypt/live/host.name/fullchain.pem;
    ssl_certificate_key /etc/letsencrypt/live/host.name/privkey.pem;

    charset UTF-8;
    #access_log  /var/log/nginx/host.access.log  main;

    location / {
        root   /usr/share/nginx/html/dir;
        index  aaa.html;
        allow all;
    }

    #error_page  404              /404.html;

    # redirect server error pages to the static page /50x.html
    #
    error_page   500 502 503 504  /50x.html;
    location = /50x.html {
        root   /usr/share/nginx/html;
    }

    #proxy the PHP scripts to Apache listening on 127.0.0.1:80
    #
    #location ~ \.php$ {
    #    proxy_pass   http://127.0.0.1;
    #}

    # pass the PHP scripts to FastCGI server listening on 127.0.0.1:9000
    #
    #location ~ \.php$ {
    #    root           html;
    #    fastcgi_pass   127.0.0.1:9000;
    #    fastcgi_index  index.php;
    #    fastcgi_param  SCRIPT_FILENAME  /scripts$fastcgi_script_name;
    #    include        fastcgi_params;
    #}

    # deny access to .htaccess files, if Apache's document root
    # concurs with nginx's one
    #
    #location ~ /\.ht {
    #    deny  all;
    #}
}

server {
    listen 80;
    server_name host.name;
    return 301 https://$host$request_uri;
}

我尝试更改程序文件的许可，但是不起作用。如何解决此错误？