looking for a custom exception

[buran]

Here is what is in the modules __init__.py file

I know what's in __init__.py - that's why I show it to you. In my code I import the module w1thermsensor and then fully reference the W1ThermSensor and NoSensorFoundError
If you prefer from w1thermsensor import W1ThermSensor, then it should be

from w1thermsensor import W1ThermSensor, NoSensorFoundError

try:
    sensor = W1ThermSensor(W1ThermSensor.THERM_SENSOR_DS18B20, '0300a27989945')
except NoSensorFoundError:
    print('Thermometer not Found')