[Help wanted, macOS] prompt_toolkit/input/vt100.py: `OSError: [Errno 45] Operation not supported`

Start with prompt_toolkit/input/vt100.py and the asyncio selector calls shown in the ptpython and fastanime tracebacks. Reproduce the failure on macOS versions below 10.6.8, then compare behavior with 10.6.8 and newer systems. Done means identifying and documenting a workable compatibility approach or confirming that no upstream change is requested.

Something does not work on macOS < 10.6.8 which leaves dependents of prompt-toolkit defunct.
The issue does not exist on 10.6.8, whether on x86, Rosetta or native powerpc.

I understand that 10.5 is old and there may not be much interest to support it and add dedicated fixes. So I do not ask to make any changes here in upstream. However, there are users of 10.4–10.5, and affected apps are end-user apps, which are desirable to have working.

Could someone suggest a solution? I can add a local patch into my fork of ports for PowerPC and use it conditionally on macOS version, so nothing gets messed up for 10.6+.

Details are below.

Example with radian:

36-137:~ svacchanda$ ptpython
Traceback (most recent call last):
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/asyncio/selector_events.py", line 256, in _add_reader
    key = self._selector.get_key(fd)
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/selectors.py", line 193, in get_key
    raise KeyError("{!r} is not registered".format(fileobj)) from None
KeyError: '0 is not registered'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/ptpython/repl.py", line 135, in run
    text = self.read()
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/ptpython/python_input.py", line 1045, in read
    result = self.app.run(pre_run=pre_run, in_thread=True)
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/prompt_toolkit/application/application.py", line 961, in run
    raise exception
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/prompt_toolkit/application/application.py", line 939, in run_in_thread
    result = self.run(
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/prompt_toolkit/application/application.py", line 978, in run
    return loop.run_until_complete(
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/asyncio/base_events.py", line 649, in run_until_complete
    return future.result()
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/prompt_toolkit/application/application.py", line 885, in run_async
    return await _run_async(f)
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/prompt_toolkit/application/application.py", line 737, in _run_async
    with self.input.raw_mode(), self.input.attach(
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/contextlib.py", line 135, in __enter__
    return next(self.gen)
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/prompt_toolkit/input/vt100.py", line 176, in _attached_input
    loop.add_reader(fd, callback_wrapper)
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/asyncio/selector_events.py", line 331, in add_reader
    self._add_reader(fd, callback, *args)
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/asyncio/selector_events.py", line 258, in _add_reader
    self._selector.register(fd, selectors.EVENT_READ,
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/selectors.py", line 523, in register
    self._selector.control([kev], 0, 0)
OSError: [Errno 45] Operation not supported

See also: https://trac.macports.org/ticket/67046

Example with fastanime:

PMG5:~ matias$ fastanime --trace anilist
[bold yellow]Welcome to FastAnime![/bold yellow] No configuration file found.
Traceback (most recent call last):
  File "/opt/local/bin/fastanime", line 8, in <module>
    sys.exit(Cli())
             ~~~^^
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.13/lib/python3.13/site-packages/fastanime/__init__.py", line 12, in Cli
    run_cli()
    ~~~~~~~^^
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.13/lib/python3.13/site-packages/click/core.py", line 1442, in __call__
    return self.main(*args, **kwargs)
           ~~~~~~~~~^^^^^^^^^^^^^^^^^
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.13/lib/python3.13/site-packages/click/core.py", line 1363, in main
    rv = self.invoke(ctx)
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.13/lib/python3.13/site-packages/click/core.py", line 1827, in invoke
    super().invoke(ctx)
    ~~~~~~~~~~~~~~^^^^^
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.13/lib/python3.13/site-packages/click/core.py", line 1226, in invoke
    return ctx.invoke(self.callback, **ctx.params)
           ~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.13/lib/python3.13/site-packages/click/core.py", line 794, in invoke
    return callback(*args, **kwargs)
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.13/lib/python3.13/site-packages/click/decorators.py", line 34, in new_func
    return f(get_current_context(), *args, **kwargs)
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.13/lib/python3.13/site-packages/fastanime/cli/cli.py", line 106, in cli
    else loader.load(cli_overrides)
         ~~~~~~~~~~~^^^^^^^^^^^^^^^
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.13/lib/python3.13/site-packages/fastanime/cli/config/loader.py", line 88, in load
    return self._handle_first_run()
           ~~~~~~~~~~~~~~~~~~~~~~^^
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.13/lib/python3.13/site-packages/fastanime/cli/config/loader.py", line 55, in _handle_first_run
    ).execute()
      ~~~~~~~^^
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.13/lib/python3.13/site-packages/InquirerPy/base/simple.py", line 330, in execute
    result = self._run()
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.13/lib/python3.13/site-packages/InquirerPy/base/complex.py", line 208, in _run
    return self.application.run()
           ~~~~~~~~~~~~~~~~~~~~^^
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.13/lib/python3.13/site-packages/prompt_toolkit/application/application.py", line 1002, in run
    return asyncio.run(coro)
           ~~~~~~~~~~~^^^^^^
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.13/lib/python3.13/asyncio/runners.py", line 195, in run
    return runner.run(main)
           ~~~~~~~~~~^^^^^^
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.13/lib/python3.13/asyncio/runners.py", line 118, in run
    return self._loop.run_until_complete(task)
           ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.13/lib/python3.13/asyncio/base_events.py", line 725, in run_until_complete
    return future.result()
           ~~~~~~~~~~~~~^^
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.13/lib/python3.13/site-packages/prompt_toolkit/application/application.py", line 886, in run_async
    return await _run_async(f)
           ^^^^^^^^^^^^^^^^^^^
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.13/lib/python3.13/site-packages/prompt_toolkit/application/application.py", line 734, in _run_async
    with self.input.raw_mode(), self.input.attach(
                                ~~~~~~~~~~~~~~~~~^
        read_from_input_in_context
        ^^^^^^^^^^^^^^^^^^^^^^^^^^
    ), attach_winch_signal_handler(self._on_resize):
    ^
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.13/lib/python3.13/contextlib.py", line 141, in __enter__
    return next(self.gen)
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.13/lib/python3.13/site-packages/prompt_toolkit/input/vt100.py", line 165, in _attached_input
    loop.add_reader(fd, callback_wrapper)
    ~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.13/lib/python3.13/asyncio/selector_events.py", line 347, in add_reader
    self._add_reader(fd, callback, *args)
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.13/lib/python3.13/asyncio/selector_events.py", line 279, in _add_reader
    self._selector.register(fd, selectors.EVENT_READ,
    ~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^
                            (handle, None))
                            ^^^^^^^^^^^^^^^
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.13/lib/python3.13/selectors.py", line 505, in register
    self._selector.control([kev], 0, 0)
    ~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^
OSError: [Errno 45] Operation not supported

Reported in https://forums.macrumors.com/threads/ppcports-the-only-ports-you-ever-need-on-a-powerpc.2462897/page-3?post=34091087#post-34091087

P. S. Please do not close the issue immediately; if there is no response for a while, it can be closed as not planned.