On Windows, the problem appears under Python 3.2.2 and 3.1.3, but not under 2.7.1. On Linux, I have not reproduced the problem on versions 2.6.3, 2.7.2, 3.1.1, or 3.2.2.

So to summarize:

  - It seems there should be a stderr flush call on the line I indicated, for symmetry with the surrounding code.
  - Even without this line, it should still be flushed automatically upon child process exit, but this doesn't happen under Windows and Python 3.x.