Fix ReadTheDocs. The formatting was a bit wonky and audioio needed

to be mocked out.

Author: tannewt

adafruit_circuitplayground/express.py

@@ -192,18 +192,15 @@ def red_led(self, value):
         self._led.value = value
 
     def play_tone(self, frequency, duration):
-        """ Produce a tone using the speaker.
+        """ Produce a tone using the speaker. Try changing frequency to change
+        the pitch of the tone.
 
         :param int frequency: The frequency of the tone in Hz
         :param float duration: The duration of the tone in seconds
 
         .. image :: /_static/speaker.jpg
 
-            The two numbers are frequency and duration. Duration is how long it
-            plays in seconds. Try changing frequency to change the pitch of the
-            tone.
-
-        ..code-block:python
+        .. code-block:: python
 
             from adafruit_circuitplayground.express import circuit
 

conf.py

@@ -20,7 +20,7 @@
                        'NeoPixel': ('https://circuitpython.readthedocs.io/projects/neopixel/en/latest/', None)}
 
 # Libraries we depend on but don't need for generating docs.
-autodoc_mock_imports = ["board", "analogio", "digitalio", "neopixel", "adafruit_thermistor"]
+autodoc_mock_imports = ["board", "analogio", "digitalio", "neopixel", "adafruit_thermistor", "audioio"]
 
 # Add any paths that contain templates here, relative to this directory.
 templates_path = ['_templates']