Bug report: test failures on s390x

## Environment

OS: Linux - Fedora Rawhide
Python version: 3.11.3
Toolkit: Qt
Qt API: PyQt5

## Description

When building the Fedora pyface package on the s390x builder I get the following build errors not seen on other architectures:

```
======================================================================
FAIL: test_array_to_image_rgb (pyface.ui.qt.util.tests.test_image_helpers.TestArrayImageHelpers.test_array_to_image_rgb)
----------------------------------------------------------------------
Traceback (most recent call last):
File "/builddir/build/BUILDROOT/python-pyface-8.0.0-1.fc39.noarch/usr/lib/python3.11/site-packages/pyface/ui/qt/util/tests/test_image_helpers.py", line 182, in test_array_to_image_rgb
self.assertTrue(all(
AssertionError: False is not true
======================================================================
FAIL: test_array_to_image_rgba (pyface.ui.qt.util.tests.test_image_helpers.TestArrayImageHelpers.test_array_to_image_rgba)
----------------------------------------------------------------------
Traceback (most recent call last):
File "/builddir/build/BUILDROOT/python-pyface-8.0.0-1.fc39.noarch/usr/lib/python3.11/site-packages/pyface/ui/qt/util/tests/test_image_helpers.py", line 203, in test_array_to_image_rgba
self.assertTrue(all(
AssertionError: False is not true
======================================================================
FAIL: test_image_to_array_rgb (pyface.ui.qt.util.tests.test_image_helpers.TestArrayImageHelpers.test_image_to_array_rgb)
----------------------------------------------------------------------
Traceback (most recent call last):
File "/builddir/build/BUILDROOT/python-pyface-8.0.0-1.fc39.noarch/usr/lib/python3.11/site-packages/pyface/ui/qt/util/tests/test_image_helpers.py", line 142, in test_image_to_array_rgb
self.assertTrue(np.all(array[:, :, 3] == 0xff))
AssertionError: False is not true
======================================================================
FAIL: test_image_to_array_rgba (pyface.ui.qt.util.tests.test_image_helpers.TestArrayImageHelpers.test_image_to_array_rgba)
----------------------------------------------------------------------
Traceback (most recent call last):
File "/builddir/build/BUILDROOT/python-pyface-8.0.0-1.fc39.noarch/usr/lib/python3.11/site-packages/pyface/ui/qt/util/tests/test_image_helpers.py", line 155, in test_image_to_array_rgba
self.assertTrue(np.all(array[:, :, 0] == 0x44))
AssertionError: False is not true
----------------------------------------------------------------------
```

## Steps to Reproduce
```
+ export ETS_TOOLKIT=qt
+ ETS_TOOLKIT=qt
+ export QT_API=pyqt5
+ QT_API=pyqt5
+ export EXCLUDE_TESTS=wx
+ EXCLUDE_TESTS=wx
+ xvfb-run /usr/bin/python3 -Xfaulthandler -s -m unittest discover -v pyface
```