Qt for Python (PySide/Shiboken)

Thanks. That's what my test suite told me, too. So for now, I've bumped the minimum required version to 6.8. For major dependencies, my tox configuration generates an environment for each major (minor) version I claim support with. The linear sweep across PySide6 revealed that 6.7 no longer works after i implemented multiData(), which takes a QModelRoleDataSpan as an argument.