Make shutil.rmtree.onexc parameter optional

[Avasam]

Noticed while adding pyright checks to setuptools (pypa/setuptools#4192)

Doc reference: https://docs.python.org/3/library/shutil.html#shutil.rmtree

I also tested locally that the parameter is indeed optional.

---

I also changed the Exception type in _OnExcCallback for baseException so it works with ExcInfo:

Argument of type "_OnExcCallback | None" cannot be assigned to parameter "onexc" of type "_OnExcCallback" in function "__call__"
  Type "_OnExcCallback | None" is incompatible with type "_OnExcCallback"
    Type "None" is incompatible with type "_OnExcCallback"

Argument 3 has incompatible type "BaseException"; expected "Exception"

def shutil_rmtree(
    path: StrOrBytesPath,
    ignore_errors: bool = False,
    onexc: shutil._OnExcCallback | None = None,
) -> None:
    if sys.version_info >= (3, 12):
        return shutil.rmtree(path, ignore_errors, onexc=onexc)

    def _handler(fn: Callable[..., Any], path: str, excinfo: ExcInfo) -> None:
        if onexc:
            onexc(fn, path, excinfo[1])

    return shutil.rmtree(path, ignore_errors, onerror=_handler)

xref pypa/setuptools#4382

[srittau]

I'm not sure why we need this and the first overload. The first overload seems redundant.

[Avasam]

Agreed, given the params are kw only and optional. Good catch!

[github-actions]

According to mypy_primer, this change has no effect on the checked open source code. 🤖🎉