utility method to handle the result of getProcessOutputAndValue

def _convertNonZeroToFailure(self, res):
        "utility method to handle the result of getProcessOutputAndValue"
        (stdout, stderr, code) = res
        if code != 0:
            raise EnvironmentError(
                'command failed with exit code %d: %s' % (code, stderr))
        return (stdout, stderr, code)