Process.wait() on Windows may not wait till process is gone

[giampaolo]

It can erroneously return sooner but the PID is still there:

Traceback (most recent call last):
  File "c:\projects\psutil\psutil\tests\test_misc.py", line 923, in test_reap_children
    reap_children()
  File "c:\projects\psutil\psutil\tests\__init__.py", line 438, in reap_children
    assert_gone(pid)
  File "c:\projects\psutil\psutil\tests\__init__.py", line 388, in assert_gone
    assert not psutil.pid_exists(pid), pid
AssertionError: 3028
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