warning-as-error causes SystemError

PySide6 does not gracefully handle warnings-as-errors, which is common for example in `pytest` to make sure errors don't creep into code. Consider this case:

>>> from PySide6.QtCore import QEvent

>>> from PySide6.QtGui import QMouseEvent

>>> from PySide6.QtCore import Qt, QPointF

>>> pos = QPointF(288.683594, 4.558000)

>>> modifier = Qt.KeyboardModifier.NoModifier

>>> QMouseEvent(QEvent.Type.MouseButtonPress, pos, Qt.MouseButton.NoButton, Qt.MouseButton.NoButton, modifier)

<stdin>:1: DeprecationWarning: Function: 'QMouseEvent.QMouseEvent(QEvent.Type type, const QPointF & localPos, Qt.MouseButton button, QFlags<Qt.MouseButton> buttons, QFlags<Qt.KeyboardModifier> modifiers, const QPointingDevice * device)' is marked as deprecated, please check the documentation for more information.

Okay, a DeprecationWarning is reasonable here. However, when treating warnings-as-errors using pytest, or in plain Python code, things go wrong. Using the code snippet above but adding these two lines before instantiating the QMouseEvent:

>>> import warnings

>>> warnings.simplefilter('error')

We get:

>>> QMouseEvent(QEvent.Type.MouseButtonPress, pos, Qt.MouseButton.NoButton, Qt.MouseButton.NoButton, modifier)

Traceback (most recent call last):

  File "<stdin>", line 1, in <module>

SystemError: /Users/runner/miniforge3/conda-bld/python-split_1661199920571/work/Objects/longobject.c:1127: bad argument to internal function

This can lead to hard-to-interpret tracebacks like:

https://dev.azure.com/mne-tools/mne-python/_build/results?buildId=22819&view=logs&jobId=d2de176e-a8da-5d2d-82f1-e561f5072d99&j=d2de176e-a8da-5d2d-82f1-e561f5072d99&t=f4deb373-ce79-59c7-15db-2653b3e8f79f