Add function to acknowledge success non-verbally

mycroft/configuration/mycroft.conf

@@ -44,7 +44,8 @@
   // File locations of sounds to play for system events
   "sounds": {
     "start_listening": "snd/start_listening.wav",
-    "end_listening": "snd/end_listening.wav"
+    "end_listening": "snd/end_listening.wav",
+    "acknowledge": "snd/acknowledge.mp3"
   },
 
   // Mechanism used to play WAV audio files

mycroft/skills/core.py

@@ -44,7 +44,9 @@ from mycroft.skills.settings import SkillSettings
 from mycroft.skills.skill_data import (load_vocabulary, load_regex, to_alnum,
                                        munge_regex, munge_intent_parser,
                                        read_vocab_file)
-from mycroft.util import camel_case_split, resolve_resource_file
+from mycroft.util import (camel_case_split,
+                          resolve_resource_file,
+                          play_audio_file)
 from mycroft.util.log import LOG
 
 MainModule = '__init__'
@@ -1648,6 +1650,26 @@ class MycroftSkill:
         for e in list(self.scheduled_repeats):
             self.cancel_scheduled_event(e)
 
+    def acknowledge(self):
+        """ Acknowledge a successful request.
+
+        This method plays a sound to acknowledge a request that does not
+        require a verbal response. This is intended to provide simple feedback
+        to the user that their request was handled successfully.
+        """
+        file = resolve_resource_file(
+            self.config_core.get('sounds').get('acknowledge'))
+
+        if not file:
+            LOG.warning("Could not find 'acknowledge' audio file!")
+            return
+
+        process = play_audio_file(file)
+        if process:
+            process.wait()
+        else:
+            LOG.warning("Unable to play 'acknowledge' audio file!")
+
 
 #######################################################################
 # FallbackSkill base class

mycroft/util/__init__.py

@@ -18,7 +18,7 @@ import socket
 import subprocess
 import pyaudio
 
-from os.path import join, expanduser
+from os.path import join, expanduser, splitext
 
 from threading import Thread
 from time import sleep
@@ -93,6 +93,36 @@ def resolve_resource_file(res_name):
     return None  # Resource cannot be resolved
 
 
+def play_audio_file(uri: str):
+    """ Play an audio file.
+
+    This wraps the other play_* functions, choosing the correct one based on
+    the file extension. The function will return directly and play the file
+    in the background.
+
+    Arguments:
+        uri:    uri to play
+
+    Returns: subprocess.Popen object. None if the format is not supported or
+             an error occurs playing the file.
+
+    """
+    extension_to_function = {
+        '.wav': play_wav,
+        '.mp3': play_mp3,
+        '.ogg': play_ogg
+    }
+    _, extension = splitext(uri)
+    play_function = extension_to_function.get(extension.lower())
+    if play_function:
+        return play_function(uri)
+    else:
+        LOG.error("Could not find a function capable of playing {uri}."
+                  " Supported formats are {keys}."
+                  .format(uri=uri, keys=list(extension_to_function.keys())))
+        return None
+
+
 def play_wav(uri):
     """ Play a wav-file.