Sorry to see that your question hasn’t received an answer yet. Unfortunately, without more information, it is unlikely that an answer for this specific issue can be provided. Generally, you would need to configure this at the web server (e.g. Apache or Nginx) level. For example, if you were using Nginx, you could create two separate server blocks to direct requests to the right app. Learn more about Nginx server blocks in this tutorial:

• How To Set Up Nginx Server Blocks (Virtual Hosts) on Ubuntu 16.04

One important thing to note is that if you installed GitLab using their omnibus packages, they bundle a Nginx installation of their own which must be configured in /etc/gitlab/gitlab.rb

The simplest way to add a new server block is to add a custom include directive. This will allow you to set up a separate Nginx config file for the Django project. In /etc/gitlab/gitlab.rb add:

nginx['custom_nginx_config'] = "include /etc/nginx/conf.d/*.conf;"

You can now create a server block for your main site in the /etc/nginx/conf.d/ directory. You can also disable the bundled Nginx all together and install the distro version if you want by adding:

nginx['enable'] = false

See here for more information on inserting custom settings into GitLab’s Nginx config.