test_file_webp_animated.py::TestFileWebpAnimation::test_write_animation_L FAILED on ppc64 #3291

Tests/test_file_webp_animated.py::TestFileWebpAnimation::test_n_frames PASSED
Tests/test_file_webp_animated.py::TestFileWebpAnimation::test_seeking PASSED
Tests/test_file_webp_animated.py::TestFileWebpAnimation::test_timestamp_and_duration PASSED
Tests/test_file_webp_animated.py::TestFileWebpAnimation::test_write_animation_L FAILED

==================================================================================================== FAILURES =====================================================================================================
__________________________________________________________________________________ TestFileWebpAnimation.test_write_animation_L ___________________________________________________________________________________

self = <test_file_webp_animated.TestFileWebpAnimation testMethod=test_write_animation_L>

    def test_write_animation_L(self):
        """
            Convert an animated GIF to animated WebP, then compare the
            frame count, and first and last frames to ensure they're
            visually similar.
            """
    
        orig = Image.open("Tests/images/iss634.gif")
        self.assertGreater(orig.n_frames, 1)
    
        temp_file = self.tempfile("temp.webp")
        orig.save(temp_file, save_all=True)
        im = Image.open(temp_file)
        self.assertEqual(im.n_frames, orig.n_frames)
    
        # Compare first and last frames to the original animated GIF
        orig.load()
        im.load()
        self.assert_image_similar(im, orig.convert("RGBA"), 25.0)
        orig.seek(orig.n_frames-1)
        im.seek(im.n_frames-1)
        orig.load()
        im.load()
>       self.assert_image_similar(im, orig.convert("RGBA"), 25.0)

Tests/test_file_webp_animated.py:60: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
Tests/helper.py:154: in assert_image_similar
    raise e
Tests/helper.py:146: in assert_image_similar
    ave_diff, epsilon))
E   AssertionError: 25.0 not greater than or equal to 57.5169012911287 :  average pixel value difference 57.5169 > epsilon 25.0000
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! Interrupted: stopping after 1 failures !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
================================================================================ 1 failed, 505 passed, 32 skipped in 41.57 seconds ================================================================================
make: *** [Makefile:81: release-test] Fehler 2