os.posix_openpt() always fails with EINVAL on OpenBSD

[serhiy-storchaka]

Bug report

os.posix_openpt() is unusable on OpenBSD — every call fails:

>>> os.posix_openpt(os.O_RDWR | os.O_NOCTTY)
OSError: [Errno 22] Invalid argument

Modules/posixmodule.c unconditionally adds O_CLOEXEC to the flags, but OpenBSD's posix_openpt(3) returns EINVAL for any flag other than O_RDWR and O_NOCTTY. The function already makes the fd non-inheritable with _Py_set_inheritable() immediately afterwards, so skip the O_CLOEXEC flag on OpenBSD.

Linked PRs

• gh-154227: Fix os.posix_openpt() on OpenBSD #154228
• [3.15] gh-154227: Fix os.posix_openpt() on OpenBSD (GH-154228) #154235
• [3.14] gh-154227: Fix os.posix_openpt() on OpenBSD (GH-154228) #154236
• [3.13] gh-154227: Fix os.posix_openpt() on OpenBSD (GH-154228) #154237