return none so pylint is happy

Author: caternuson

adafruit_seesaw/seesaw.py

@@ -457,7 +457,7 @@ def _get_eeprom_i2c_addr(self):
         elif chip_id in (_SAMD09_HW_ID_CODE,):
             return 0x3F
         else:
-            raise RuntimeError("Unknown chip id", hex(chip_id))
+            return None
 
     def set_i2c_addr(self, addr):
         """Store a new address in the device's EEPROM and reboot it."""