'``run()`` raises ``IOError`` if subprocess has non-zero exit code.'

def test_run_bad_exit(self):

    node = ProcessNode(initial_command_arguments=[])
    nonexistent = self.mktemp()
    try:
        with node.run(['ls', nonexistent]):
            pass
    except IOError:
        pass
    else:
        self.fail('No    IOError')
