For various reasons I happened to run 'python -m test.regrtest' on my Gentoo installed Python. For 2.5.4 only test_tarfile failed (it tries to write into the read-only installed test directory). On 2.6.2 test_tarfile passes, but other test suites, including test_distutils, do not.
So this posting is a general reminder that the tests should not make assumptions about the writabilty of the test directory (or, for that matter, of the CWD).
When I get time I'll file bugs on the particular failures I'm seeing, after I do an install from checkout.