Continuing to work through test suite failures found when building on the Fedora ppc64 arch (big-endian) but not on little-endian arches. Two failures:

matplotlib.tests.test_quiver.test_barbs.test
matplotlib.tests.test_transforms.test_pre_transform_plotting.test

seem to be caused by differences in the lengths of 'barbs' on 'quivers' - the former is a test specific to such barbs, the latter includes a figure with some barbs as part of a larger test. In both cases, the lengths of the barbs come out subtly differently on ppc64:

barbs_test_image GOT:
barbs_test_image EXPECTED:
pre_transform_data GOT:
pre_transform_data EXPECTED:

the difference is quite subtle, it helps to A/B the images quickly in an image viewer. AFAICS, in all cases where the lengths are visibly different, the barbs actually produced are slightly shorter than expected.