Tests failure on s390x

We update pyside 2 in Debian to version 5.13.2

During the build we run the tests with the following command:

xvfb-run python3 testrunner.py test

It uses Python 3.7

The test suite fails on s390x:

https://buildd.debian.org/status/fetch.php?pkg=pyside2&arch=s390x&ver=5.13.2-1&stamp=1574200670&raw=0

Failure log:

RUN 1: Start 118: QtCore_qbytearray_test
RUN 1: 118/456 Test #118: QtCore_qbytearray_test ..........................***Failed 0.09 sec
RUN 1: .........FF...........
RUN 1: ======================================================================
RUN 1: FAIL: testSliceAssignmentByteArray (_main_.QByteArraySliceAssignment)
RUN 1: ----------------------------------------------------------------------
RUN 1: Traceback (most recent call last):
RUN 1: File "/<<PKGBUILDDIR>>/sources/pyside2/tests/QtCore/qbytearray_test.py", line 260, in testSliceAssignmentByteArray
RUN 1: self.assertEqual(b, py3k.b('012CBA6789'))
RUN 1: AssertionError: PySide2.QtCore.QByteArray(b'0126789') != b'012CBA6789'
RUN 1:
RUN 1: ======================================================================
RUN 1: FAIL: testSliceAssignmentBytes (_main_.QByteArraySliceAssignment)
RUN 1: ----------------------------------------------------------------------
RUN 1: Traceback (most recent call last):
RUN 1: File "/<<PKGBUILDDIR>>/sources/pyside2/tests/QtCore/qbytearray_test.py", line 209, in testSliceAssignmentBytes
RUN 1: self.assertEqual(b, py3k.b('012CBA6789'))
RUN 1: AssertionError: PySide2.QtCore.QByteArray(b'0126789') != b'012CBA6789'
[...]

RUN 1: Start 428: QtQml_qquickitem_grabToImage
RUN 1: 428/456 Test #428: QtQml_qquickitem_grabToImage ....................***Failed 0.33 sec
RUN 1: QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-buildd'
RUN 1: qt.qpa.xcb: QXcbConnection: XCB error: 2 (BadValue), sequence: 193, resource id: 18, major code: 131 (Unknown), minor code: 46
RUN 1: F
RUN 1: ======================================================================
RUN 1: FAIL: testQQuickItemGrabToImageSharedPointer (_main_.TestGrabToSharedPointerImage)
RUN 1: ----------------------------------------------------------------------
RUN 1: Traceback (most recent call last):
RUN 1: File "/<<PKGBUILDDIR>>/sources/pyside2/tests/QtQml/qquickitem_grabToImage.py", line 75, in testQQuickItemGrabToImageSharedPointer
RUN 1: self.assertEqual(self.grabbedColor, blueColor)
RUN 1: AssertionError: PySide2.QtGui.QColor.fromRgbF(1.000000, 1.000000, 0.000000, 0.000000) != PySide2.QtGui.QColor.fromRgbF(0.000000, 0.000000, 1.000000, 1.000000)

[...]

BFAIL BFAIL BFAIL BFAIL BFAIL shiboken2:smart::smart_pointer Keep blacklisting ;-(
FAIL! FAIL! FAIL! FAIL! FAIL! pyside2:QtCore::qbytearray_test Newly detected Real test failure!
BFAIL BFAIL BFAIL BFAIL BFAIL pyside2:QtCore::qflags_test Keep blacklisting ;-(
FAIL! FAIL! FAIL! FAIL! FAIL! pyside2:QtQml::qquickitem_grabToImage Newly detected Real test failure!
BFAIL BFAIL BFAIL BFAIL BFAIL pyside2:QtScriptTools::debugger_test Keep blacklisting ;-(