'ImportError: DLL load failed while importing xxxxxxx: The filename or extension is too long' with LongPathsEnabled

Bug report

Bug description:

Python 3.11.9

In Python there there is a known limitation on Windows for paths being limited at 260 symbols, unless LongPathsEnabled is set, see https://docs.python.org/3/using/windows.html#removing-the-max-path-limitation.

Without that registry key set import of module at long path fails with ModuleNotFoundError: No module named 'xxxxxxxxx' or opening file fails with FileNotFoundError: [Errno 2] No such file or directory. With registry key set the limit is extended and 260 symbols long paths are working fine.

The issue I've found that importing binary Python extension seems to break on long paths (250 symbols seems to be max length) even with LongPathsEnabled, see the snippet below.
To reproduce this, you can setup some very long path (>250 symbols) in your site-packages and put in that directory one empty .py file (in my case it's "yyyy...yyyyyyyyyyy.py") and some .pyd file that it's importing fine without any other binary dependencies - in my case I was using _yaml.cp311-win_amd64.pyd I got from https://pypi.org/project/PyYAML/#files.

# Importing just .py module.
import xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx.yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy as script
print(len(script.__file__)) # 298. Doesn't seem to have limit at 250-260 symbols.
# Importing .pyd.
import xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx._yaml as yaml
print(len(yaml.__file__)) # 250. seems to be the max.

Found this issue working with Blender (related issue) - Blender comes with it's own Python and there's an option to store some of Blender addons dependencies next to blender.exe, so it can be virtually anywhere on the computer and paths can get very long.

CPython versions tested on:

3.11

Operating systems tested on:

Windows

Linked PRs

• gh-156759

首先在 Windows 上進行重現，使用長度超過 250 個字元的 site-packages 路徑、一個空的 .py 模組以及 _yaml.cp311-win_amd64.pyd 擴充功能。比較在啟用 LongPathsEnabled 時一般模組匯入與二進位擴充功能匯入的情況，並檢視連結的 PR gh-156759。當二進位 Python 擴充功能能夠在 Windows 上從這些長路徑成功匯入時，即表示完成。