In investigating issue 9993, I noticed that test_shutil wants to test things that require cross-file-system links, and arranges to have such links by creating a files and directories in the cwd and using tempfile.  Presumably the hope (and the comments make it clear it is a hope) is that frequently these will be different filesystems.  This is likely to be true on some systems (principally those that put /tmp on a memory file system), there is no guarantee that it is true for any system in the buildbot fleet (for example).

In addition, relatively recent changes to regrtest ensure that when the tests are run for an installed Python, the cwd is *guaranteed* to be in the same file system as things created by tempfile, since in that case the tempfile module is used by regrtest to run all tests in a temporary cwd.

It is this latter case that most concerns me and prompts this bug report, since a distribution should be able to reasonably expect that running the tests after installation (either real or sandboxed) should in fact test python on the target system.

Unfortunately I don't currently have a suggestion for how to reliably create a cross-file-system link for testing purposes.