Exit if process is a zombie process

[astrofrog]

@embray - could you try this branch?

[embray]

I just tried almost exactly that, and that should do it I think. It's still just odd that it's needed, since the psutil docs say NoSuchProcess is raised when the process is in zombie state, but maybe not all its methods actually do that...

[embray]

I see the problem in psutil. The way it implements Process.get_cpu_times and Process.get_memory_info on Linux are to read them right out of /proc/<pid>/stat[m] which will work just fine for zombie processes--it doesn't check the process status before returning results from those calls so it never has an opportunity to raise NoSuchProcess. I'll send them a patch :)

This also explains why you've never seen it, as it's a Linux-specific issue.

[astrofrog]

@embray - ah I see, thanks for looking into it! In the mean time, does this PR provide a workaround?

[embray]

Yes, this workaround is fine for now. See also https://code.google.com/p/psutil/issues/detail?id=467