Oh, I have not realized the debug output was useful in this way 
. UI will be improved in pynitrokey. I unfortunately do not see why Udev rules were not working for you.
I think there is no automated way as of this moment. You can check it by:
- Registering at test site, like https://u2f.bin.coffee/
- Running signing (should pass)
- Running factory reset on the device
- Running signing again (should fail)