Qt installwizard: raise UserCancelled if user clicks cancel (the wizard was hanging instead of terminating)

electrum/gui/qt/installwizard.py

@@ -109,6 +109,8 @@ def wizard_dialog(func):
             except GoBack:
                 if not wizard.can_go_back():
                     wizard.close()
+                    raise UserCancelled
+                else:
                     # to go back from the current dialog, we just let the caller unroll the stack:
                     raise
             # next dialog