def spawn(self, cmd, expect_timeout=10.0):
        """Run a command using pexpect.

        The pexpect child is returned.
        """
        pexpect = pytest.importorskip("pexpect", "3.0")
        if hasattr(sys, 'pypy_version_info') and platform.machine() in '64':
            pytest.skip("pypy-64 bit not supported")
        if sys.platform == "darwin":
            pytest.xfail("pexpect does not work reliably on darwin?!")
        if sys.platform.startswith("freebsd"):
            pytest.xfail("pexpect does not work reliably on freebsd")
        logfile = self.tmpdir.join("spawn.out").open("wb")
        child = pexpect.spawn(cmd, logfile=logfile)
        self.request.addfinalizer(logfile.close)
        child.timeout = expect_timeout
        return child
dataset/ETHPy150Open pytest-dev/pytest/_pytest/pytester.py/Testdir.spawn/swapped operands of `in`