TST: TestQuantityReshapeFuncs.test_flat_attributes failed with AssertionError on s390x (big-endian)

Example log: https://github.com/astropy/astropy/runs/2708622607?check_suite_focus=true

Last week’s run was successful (https://github.com/astropy/astropy/runs/2653579480?check_suite_focus=true) on 2021-05-24.

________________ TestQuantityReshapeFuncs.test_flat_attributes _________________

self = <astropy.units.tests.test_quantity_array_methods.TestQuantityReshapeFuncs object at 0x42b00b16a0>

    def test_flat_attributes(self):
        """While ``flat`` doesn't make a copy, it changes the shape."""
        q = np.arange(6.).reshape(3, 1, 2) * u.m
        qf = q.flat
        # see TestQuantityArrayCopy.test_flat for tests of iteration
        # and slicing and setting. Here we test the properties and methods to
        # match `numpy.ndarray.flatiter`
        assert qf.base is q
        # testing the indices -- flat and full -- into the array
        assert qf.coords == (0, 0, 0)  # to start
        assert qf.index == 0
        # now consume the iterator
        endindices = [(qf.index, qf.coords) for x in qf][-2]  # next() oversteps
>       assert endindices[0] == 5
E       assert 0 == 5

astropy/units/tests/test_quantity_array_methods.py:138: AssertionError

Could this be related to #11796 , @mhvk or @nstarman ?

Also see #11783, numpy/numpy#19153

[mhvk]

Yes, hopefully, things will just work with numpy-dev!

[pllim]

Looks like numpy/numpy#19153 is marked as a bug and slated to be fixed in Numpy 1.22. So, for now, perhaps we can xfail this test for numpy<=1.21 in the s390x job only?