Review of #131847: the retry ran for every rmtree failure on every OS.
On POSIX an unreadable directory hands the callback os.open, and
func(path) raised TypeError (missing flags), which escaped the OSError
set-aside path and failed an install that had already published. And
os.chmod followed a symlink inside an unwritable directory, rewriting
the mode of a file outside the tree to 0200.
The retry now only fires for a PermissionError from os.unlink/os.rmdir
on Windows, and clears the link's own attribute where chmod can follow
links; everything else raises as plain rmtree does.
eb7e862032