Lucaschess not starting up : Ubuntu 18.04

[Arunachala-Ramana]

Lucaschess not starting up after I tried to change the background color. Please help.

Traceback (most recent call last):
  File "./Lucas.py", line 46, in <module>
    Code.Init.init()
  File "./Code/Init.py", line 25, in init
    resp = Gui.lanzaGUI(mainProcesador)
  File "./Code/QT/Gui.py", line 80, in lanzaGUI
    qpalette = QtGui.QPalette(QtGui.QPalette.Dark)
TypeError: QPalette(): argument 1 has unexpected type 'ColorRole'
Traceback (most recent call last):
  File "./Lucas.py", line 46, in <module>
    Code.Init.init()
  File "./Code/Init.py", line 25, in init
    resp = Gui.lanzaGUI(mainProcesador)
  File "./Code/QT/Gui.py", line 80, in lanzaGUI
    qpalette = QtGui.QPalette(QtGui.QPalette.Dark)
TypeError: QPalette(): argument 1 has unexpected type 'ColorRole''