AppImage breaks nested launching from Python

Begin with the extracted AppImage and ./AppRun reproduction, then inspect scc/scripts.py around run_binary at line 28. Compare the nested launch behavior under Python 3.12 and 3.13, including the ./env failure, and verify that the completed change works for both direct and Python-launched binaries inside the AppImage.

The problem demonstrated on an extracted AppImage:

[0] % ./AppRun                                            
Traceback (most recent call last):
  File "/home/c0rn3j/Downloads/appimage-trixie-amd64/squashfs-root/usr/bin/scc", line 8, in <module>
    sys.exit(main())
             ~~~~^^
  File "/home/c0rn3j/Downloads/appimage-trixie-amd64/squashfs-root/usr/lib/python3.13/site-packages/scc/scripts.py", line 412, in main
    sys.exit(command(sys.argv[0], sys.argv[2:]))
             ~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/c0rn3j/Downloads/appimage-trixie-amd64/squashfs-root/usr/lib/python3.13/site-packages/scc/scripts.py", line 47, in cmd_gui
    return run_binary("sc-controller", argv)
  File "/home/c0rn3j/Downloads/appimage-trixie-amd64/squashfs-root/usr/lib/python3.13/site-packages/scc/scripts.py", line 30, in run_binary
    child = subprocess.Popen([binary] + argv)
  File "/home/c0rn3j/Downloads/appimage-trixie-amd64/squashfs-root/usr/lib/python3.13/subprocess.py", line 1039, in __init__
    self._execute_child(args, executable, preexec_fn, close_fds,
    ~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
                        pass_fds, cwd, env,
                        ^^^^^^^^^^^^^^^^^^^
    ...<5 lines>...
                        gid, gids, uid, umask,
                        ^^^^^^^^^^^^^^^^^^^^^^
                        start_new_session, process_group)
                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/c0rn3j/Downloads/appimage-trixie-amd64/squashfs-root/usr/lib/python3.13/subprocess.py", line 1857, in _execute_child
    self._posix_spawn(args, executable, env, restore_signals, close_fds,
    ~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
                      p2cread, p2cwrite,
                      ^^^^^^^^^^^^^^^^^^
                      c2pread, c2pwrite,
                      ^^^^^^^^^^^^^^^^^^
                      errread, errwrite)
                      ^^^^^^^^^^^^^^^^^^
  File "/home/c0rn3j/Downloads/appimage-trixie-amd64/squashfs-root/usr/lib/python3.13/subprocess.py", line 1801, in _posix_spawn
    self.pid = os.posix_spawn(executable, args, env, **kwargs)
               ~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
FileNotFoundError: [Errno 2] No such file or directory: '/home/c0rn3j/Downloads/appimage-trixie-amd64/squashfs-root/usr/bin/sc-controller'

Now, changing the usr/bin/env python in sc-controller to /usr/bin/env python solves this, because it no longer tries to load the AppImage-castrated env binary that relies on lib64/ld-linux-x86-64.so.2 to exist, but we're not in runtime/compat where it resides.

So we get this wonderful error when launching directly, and the same issue will break the binary when launched through Python:

./env 
zsh: no such file or directory: ./env

Now, the scripts.py is launching it this way: https://github.com/C0rn3j/sc-controller/blob/5a8e3025f75c214a54db05d438e2bbab015cf057/scc/scripts.py#L28

This works on Python 3.12 and earlier, but not Python 3.13, since that now uses posix_spawn() by default in this situation - https://docs.python.org/3/whatsnew/3.13.html#subprocess

A workaround is to preface subprocess.Popen calls with:

subprocess._USE_POSIX_SPAWN = False

Or replacing the shebang with the host's /usr/bin/env, if env is all you use in your shebangs.

What am I supposed to do here?