Error in shipping Django Zipapp

Following the Django zipapp walk through in the documentation [here](https://shiv.readthedocs.io/en/latest/django.html) produces
NotADirectoryError: [Errno 20] for Django 3.1

Start by reproducing the Django zipapp walkthrough at the linked documentation page with Django 3.1 and capture the full NotADirectoryError traceback. Trace the failing packaging or execution step to the relevant entry point; done means the documented walkthrough completes successfully without the error.

Written by the indexing model from the issue text.