Change logging level of warning

This was too confusing for users, so
downgrade the level to debug.

Author: G3zz

sense_hat/sense_hat.py

@@ -97,7 +97,7 @@ def __init__(
         try:
             self._colour = ColourSensor()
         except Exception as e:
-            logging.warning(e)
+            logging.debug(e)
             pass
 
     ####