Running in sub directory causes 403 error

I want to run WordPress only in sub directory ‘news’,
so I’ve written in app.yaml

- url: /news/(.*\.(htm|html|css|js))$
  static_files: wordpress/\1

….and so on,

and in wp-config.php

define( 'WP_SITEURL', $protocol_to_use . $_SERVER['HTTP_HOST'].'/news');
define( 'WP_HOME', $protocol_to_use . $_SERVER['HTTP_HOST'] .'/news');

But in this case, I couldn’t upload files.
It causes 403 error and error message says ‘HTTP error’.

How can I avoid it, or
is it not supporsed to be used in this way?

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