My futher discovery is:
The broblem looks like to be in the backlight module. Each time I import the module I get the message.
So where do I have to correct?
Or is there a new backlight module?
This error lookslike that at: Display-O-Tron HAT i2c problem
I have tried to reactivate i2c and reboot and run the backlight.py-program and still get the error.