ads1x15.py: define Pin if import fails

Author: ilario

adafruit_ads1x15/ads1x15.py

@@ -25,6 +25,10 @@
     from busio import I2C
     from microcontroller import Pin
 except ImportError:
+    # define Pin to avoid the error:
+    #   def read(self, pin: Pin, is_differential: bool = False) -> int:
+    #   NameError: name 'Pin' is not defined
+    Pin = None
     pass
 
 _ADS1X15_DEFAULT_ADDRESS = const(0x48)