502 Bad Gateway when following Django Nginx Ubuntu 16.04 guide

I’m following this guide. The development methods for serving my Django app work (using python manage.py runserver and gunicorn --bind 0.0.0.0:8000 myproject.wsgi:application), but when I set up the systemd and Nginx configuration files, I just get a 502 Nginx error page. I believe that Nginx is supposed to create the relevant .sock file at some point, but I don’t see one in my project directory.

Ultimately, I would actually like my Django app to be served on a subdirectory of the domain, like mysite.com/sub/, since there is a website currently being served on the root domain.

Your help is greatly appreciated,

Nathan