gui branch does not work with ipython3

thomas@dop407 lofar_stager_api (gui) 116: ipython3 stager.py
Python 3.7.3 (default, Apr  3 2019, 05:39:12)
Type "copyright", "credits" or "license" for more information.

IPython 5.8.0 -- An enhanced Interactive Python.
?         -> Introduction and overview of IPython's features.
%quickref -> Quick reference.
help      -> Python's own help system.
object?   -> Details about 'object', use 'object??' for extra details.
2019-09-25 16:01:36.614007 - stager_access: Parsing user credentials from "/home/thomas/.stagingrc"
2019-09-25 16:01:36.614325 - stager_access: Creating proxy
---------------------------------------------------------------------------
ImportError                               Traceback (most recent call last)
/home/thomas/workspace.astron/git/lofar_stager_api/stager.py in <module>()
      7 logging.basicConfig(format=FORMAT, level=logging.DEBUG)
      8 logger = logging.getLogger(__name__)
----> 9 from lib.ui_mainwindow import *
     10 import threading
     11 from PySide2.QtCore import QTimer, QObject, SIGNAL, Signal, Slot

/home/thomas/workspace.astron/git/lofar_stager_api/lib/ui_mainwindow.py in <module>()
      9 # WARNING! All changes made in this file will be lost!
     10
---> 11 from PySide2 import QtCore, QtGui, QtWidgets
     12
     13 class Ui_MainWindow(object):

/usr/lib/python3/dist-packages/IPython/external/qt_loaders.py in load_module(self, fullname)
     54     Importing %s disabled by IPython, which has
     55     already imported an Incompatible QT Binding: %s
---> 56     """ % (fullname, loaded_api()))
     57
     58 ID = ImportDenier()

ImportError:
    Importing PySide2 disabled by IPython, which has
    already imported an Incompatible QT Binding: pyqt5