capture stdout and stderror from within a Windows Service?

[Chris Curvey]

I'm trying to get this invocation right, and it is escaping me.  How
can I capture the stdout and stderr if I launch a subprocess using
subprocess.check_call()?  The twist here is that the call is running
from within a Windows service.

I've tried:

check_call("mycmd.exe", stdout=subprocess.PIPE)  [raises an exception
"An integer is required"]

check_call("mycmd.exe", stdout=file("c:\\temp\\foobar.txt", "w"))
[raises an exception "An integer is required"]