Path.copy fails on filesystems where FICLONE returns EPERM instead of falling back #161241

Path.copy() on Linux tries FICLONE first. On filesystems where that ioctl is blocked it returns EPERM (e.g. overlayfs in containers; SELinux-blocked ioctl is a known precedent). pathlib/_os.py copyfileobj only falls back on EBADF, EOPNOTSUPP, ETXTBSY, EXDEV, so the copy fails with PermissionError even though a regular copy works — shutil.copy() succeeds on the same files.

Reproducer: build main, then Path('a.txt').copy('c.txt') on such a filesystem (also reproducible by making _ficlone raise EPERM).

Proposed fix: add EPERM to the _ficlone fallback list.

Linked PRs

• gh-161241: Fall back when FICLONE fails with EPERM in pathlib copyfileobj #161244