Sometimes, each run of test_functools leaks exactly 1 memory block, even when the whole test is "re-run in verbose mode". Sometimes, it doesn't leak.

https://buildbot.python.org/all/#/builders/80/builds/550

test_functools leaked [1, 1, 1] memory blocks, sum=3
Re-running test 'test_functools' in verbose mode
test_functools leaked [1, 1, 1] memory blocks, sum=3

Maybe the problem comes from 

Example on Linux:

$ ./python -m test -F -r -j1 -R 3:3 test_functools  
Using random seed 3891892
Run tests in parallel using 1 child processes
0:00:01 load avg: 2.38 [  1] test_functools passed
beginning 6 repetitions
123456
......
(...)
0:00:06 load avg: 2.27 [  6] test_functools passed
beginning 6 repetitions
123456
......
0:00:07 load avg: 2.27 [  7/1] test_functools failed
beginning 6 repetitions
123456
......
test_functools leaked [1, 2, 1] memory blocks, sum=4
0:00:08 load avg: 2.27 [  8/1] test_functools passed
beginning 6 repetitions
123456
......

== Tests result: FAILURE ==

7 tests OK.

1 test failed:
    test_functools

Total duration: 8 sec 333 ms
Tests result: FAILURE