make play_mp3 unsupported in the express module

FoamyGuy · FoamyGuy · commit 6232174fd743 · 2020-06-15T19:24:51.000-05:00
diff --git a/adafruit_circuitplayground/express.py b/adafruit_circuitplayground/express.py
@@ -87,6 +87,7 @@ def _unsupported(self):
     # Express, they will result in the NotImplementedError raised in the property above.
     sound_level = _unsupported
     loud_sound = _unsupported
+    play_mp3 = _unsupported
 
 
 cpx = Express()  # pylint: disable=invalid-name
