Crash on startup: ModuleNotFoundError: No module named 'six' under Python 3.13 environment

[myoule]

Description

Hi, I encountered a critical crash when running linuxpop inside a Flatpak / containerized environment. The application fails to start because the python-xlib library requires the six dependency, which is currently missing from the runtime environment.

Since the application runs in a read-only environment, users cannot manually install it via pip.

Traceback / Error Log

Traceback (most recent call last):
  File "/app/share/linuxpop/main.py", line 794, in <module>
    sys.exit(main())
             ~~~~^^
  File "/app/share/linuxpop/main.py", line 753, in main
    app = App(enable_tray=not args.no_tray)
  File "/app/share/linuxpop/main.py", line 185, in __init__
    self._start_watcher()
    ~~~~~~~~~~~~~~~~~~~^^
  File "/app/share/linuxpop/main.py", line 380, in _start_watcher
    self.watcher = get_backend().make_selection_watcher(
                   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^
        on_selection,
        ^^^^^^^^^^^^^
        int(self.settings.get("selection_debounce_ms")),
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    )
    ^
  File "/app/share/linuxpop/platform_backend/x11.py", line 180, in make_selection_watcher
    from watcher import SelectionWatcher
  File "/app/share/linuxpop/watcher.py", line 14, in <module>
    from Xlib import display
  File "/app/lib/python3.13/site-packages/Xlib/display.py", line 26, in <module>
    from six import create_unbound_method
ModuleNotFoundError: No module named 'six'

Expected Behavior

The app should start normally without missing basic python dependencies.

Environment

• OS / Distribution: Linux Mint 22.3
• Desktop Environment: Cinnamon (64-bit)
• Display Server: X11
• Python Version: 3.13
• Installation Method: Flatpak / Container

Suggested Fix

Please consider adding python3-six or the six wheel package into the Flatpak manifest (.yml) modules list before building the main application, or vendor it directly into the backend dependencies.

Thank you for maintaining this great project!