The expected side effect of this change is that hunting memory leaks in regrtest (python -m test) may get more noise.

I ran the Python test suite using "./python -m test -R 3:3": test_nntplib, test_tools and test_unittest failed.

Run alone, test_tools still fails:
-------------
$ ./python -m test -R 3:3 test_tools
0:00:00 [1/1] test_tools
beginning 6 repetitions
123456
......
test_tools leaked [0, 5, 20] references, sum=25
test_tools leaked [0, 1, 4] memory blocks, sum=5
test_tools took 44 sec
1 test failed:
    test_tools
Total duration: 0:00:45
-------------

But if I run test_tools one more time, it doesn't fail anymore...

Example of two sequential runs using two processes:
-------------
$ ./python -m test -R 3:3 test_tools
Run tests sequentially
0:00:00 [1/1] test_tools
beginning 6 repetitions
123456
......
test_tools took 44 sec
1 test OK.
Total duration: 0:00:44

$ ./python -m test -R 3:3 test_tools
Run tests sequentially
0:00:00 [1/1] test_tools
beginning 6 repetitions
123456
......
test_tools leaked [2, 0, 10] references, sum=12
test_tools leaked [0, 0, 3] memory blocks, sum=3
test_tools took 43 sec
1 test failed:
    test_tools
Total duration: 0:00:44
-------------

test_nntplib doesn't fail anymore when run alone.

Oh, and test_unittest failure doesn't seem related to my change: "./python -m test -R 3:3 test_unittest" already fails without my change.