> test_idle leaked [1, 1, 1, 1] memory blocks, sum=4
While reference leaks are more or less stable, the check on memory blocks is fragile.
I'm unable to reproduce your issue on Linux. I tested "./python -m test -R 3:3 -u gui -v test_idle". If you have a reproductible failure, please open a new issue since this one is closed.
If you consider that it's a recent regression, you can go back in history using git checkout <old sha1>, or even git bisect.
If you open a new issue, you may want to use "python -m test.bisect ..." to identify which test leaks memory blocks.