Defer `import warnings` in pathlib

[barneygale]

As of GH-118793, the warnings module is used only once in pathlib, by PurePath.is_reserved(). We should be able to move the import warnings line into that method. But beware! Doing so seems to cause a failure in test_io, which needs further investigation.

Linked PRs

• gh-119049: Fix incorrect usage of GET_WARNINGS_ATTR #119063
• [3.13] gh-119049: Fix incorrect display of warning which is constructed by C API (GH-119063) #119106
• gh-119049: Defer import warnings in pathlib._locals #119111
• [3.12] gh-119049: Fix incorrect display of warning which is constructed by C API (GH-119063) #119119

[Eclips4]

But beware! Doing so seems to cause a failure in test_io, which needs further investigation.

I've written #119063 to address this. FYI, this is not related to pathlib :)

[barneygale]

Woot! Thank you @Eclips4 for sorting this :)