Message 354926 - Python tracker

I can recreate this manually by running regrtest.py against test_pty.  Crashes with any "-j#" option, but fine when run sequentially.  Removing the process group change avoids the crash.

With the process group change in place, the trigger point appears to be the final "os.close(master_fd)" in PtyTest.test_basic.  Commenting that out avoids the crash.