Cannot import an extension module if its path is not encodable in UTF-8

Bug report

Importing an extension module fails with UnicodeEncodeError if its path contains characters unencodable in UTF-8, e.g. surrogate escapes of a file name undecodable in the filesystem encoding.

$ .../nd\udcffwt/python -c "import _json"
Traceback (most recent call last):
  File "<string>", line 1, in <module>
UnicodeEncodeError: 'utf-8' codec can't encode character '\udcff' in position 45: surrogates not allowed

As a result, CPython cannot be run in a directory whose name contains undecodable bytes, and cannot even be built there -- make fails in checksharedmods. On 3.13 and 3.14 every import of a shared extension module from such a path fails.

The cause is the key of the extensions cache: hashtable_key_from_2_strings() in Python/import.c encodes the module file name with _PyUnicode_AsUTF8NoNUL(). It was added in gh-105699.

The raw content of the strings (UCS1, UCS2 or UCS4) can be used for the key instead of the UTF-8 encoding.

Linked PRs

• gh-155249

从 Python/import.c 中的 hashtable_key_from_2_strings() 开始，issue 将扩展模块文件名的 UTF-8 编码确定为原因。检查链接的 PR gh-155249，以及报告中描述的 checksharedmods 失败。完成结果应包括：能够从包含无法解码的文件名字节的路径成功导入和构建扩展模块。