Wrong Qt5 package name prevents clients from running on new installs

[ataffanel]

When testing a new VM, the client did not start anymore. The error message is about import of PyQt5.QtGui.QMessageBox not existing.

A bit of investigation shows that all the widget moved to PyQt5.QtWidgets so changing QtGui into QtWidgets solves the ptoblem.

The same client using the same version of pyqt5 works on my machine running Ubuntu 20.04 but not anymore on newly installed VM ruining Ubuntu 20.04 and this while using the same versions on PyQt5 from Pypi. I cannot explain that, but since fixing the package name is the correct fix and fixes the situation, lets do that.