Adding 404 page to a custom path


I would like to use a custom 404.html which is generated by Sphinx, but the file is not inserted on root level.

To be more specific, this file should be used for default 404 error.

However, it does not, so I’ve added a default 404.html to redict:

Is there some way to do it, without that file on the root level? (I’m not using Jekyll).