Include a PYTHONPATH extension allowing for user-space packages #30
Description
What is the problem or limitation you are having?
The app script currently sets a PYTHONPATH that includes the app and app_packages paths, plus the stdlib.
These paths are all inside the application bundle, which the user does not have access to modify.
If a user wants to add additional files to the PYTHONPATH (e.g., if you were building a "Jupyter Notebook" app, and wanted the user to be able to access user-installed packages), you can't install that code into app or app_packages.
Describe the solution you'd like
The app script should include an XDG compliant user path as part of the standard app path. This is probably:
~/.local/share/<app name>/user_packages
Describe alternatives you've considered
Don't allow user-installed packages.
Additional context
See beeware/briefcase-linux-system-template#3 and beeware/briefcase-linux-flatpak-template#18 for analogous problems.