Debugging test with subprocesses does not work

[karthiknadig]

1. Clone and open ptvsd folder.
2. wait for the tests for load in the test explorer.
3. Hit debug test on any of the tests.

[DonJayamanne]

Need to enable subProcess when debugging.
Works with that, but requires extension changes.

[zchrissirhcz]

Hi, how's the issue and patch going? I'm debugging a multiprocessing program, and I've tried python3.5, python3.6 and python3.7. All of these three version python failed when debugging in VSCode. I wonder if this can be fixed soon? Correct me if I'm wrong, thanks.