Refining new "listening" sound mechanism

This adds several refinements to the listening sound mechanism added by:
* Added a default sound file
* Allowing various ways to override "resource files" for customization
* Moved the sound configuration path from "confirm_ding" to
  "sounds" > "start_listening"
* Also added "sounds" > "end_listening" configuration for the future

This submission adds the new mycroft.util.resolve_resource_file(res_name)
method.  This method takes a name such as "snd/start_listening.wav" and
looks (in order):
* For an absolute path <res_name>
* For ~/.mycroft/<res_name>
* For /opt/mycroft/<res_name>
* For mycroft/res/<res_name> within the source package

mycroft/client/speech/main.py

@@ -27,11 +27,9 @@ from mycroft.identity import IdentityManager
 from mycroft.messagebus.client.ws import WebsocketClient
 from mycroft.messagebus.message import Message
 from mycroft.tts import TTSFactory
-from mycroft.util import kill, play_wav
+from mycroft.util import kill, play_wav, resolve_resource_file
 from mycroft.util.log import getLogger
 
-from os.path import expanduser
-
 logger = getLogger("SpeechClient")
 ws = None
 tts = TTSFactory.create()
@@ -44,10 +42,12 @@ config = ConfigurationManager.get()
 def handle_record_begin():
     logger.info("Begin Recording...")
 
-    # If enabled, play a wave file with a short sound to indicate recording has
+    # If enabled, play a wave file with a short sound to audibly
-    # begun.
+    # indicate recording has begun.
     if config.get('confirm_listening'):
-        play_wav(expanduser(config.get('confirm_ding')))
+        file = resolve_resource_file(config.get('sounds').get('start_listening'))
+        if file:
+            play_wav(file)
 
     ws.emit(Message('recognizer_loop:record_begin'))
 
@@ -105,6 +105,7 @@ def handle_speak(event):
     else:
         mute_and_speak(utterance)
 
+
 def handle_sleep(event):
     loop.sleep()
 

mycroft/configuration/mycroft.conf

@@ -3,8 +3,11 @@
   "system_unit": "metric",
   "time_format": "half",
   "date_format": "MDY",
-  "confirm_listening": false,
+  "confirm_listening": true,
-  "confirm_ding": "~/.mycroft/ding.wav",
+  "sounds": {
+    "start_listening": "snd/start_listening.wav",
+    "end_listening": "snd/end_listening.wav"
+  },
   "location": {
     "city": {
       "code": "Lawrence",

mycroft/util/__init__.py

@@ -28,6 +28,52 @@ from os.path import dirname
 __author__ = 'jdorleans'
 
 
+def resolve_resource_file(res_name):
+    """Convert a resource into an absolute filename.
+
+    Resource names are in the form: 'filename.ext'
+    or 'path/filename.ext'
+
+    The system wil look for ~/.mycroft/res_name first, and
+    if not found will look at /opt/mycroft/res_name,
+    then finally it will look for res_name in the 'mycroft/res'
+    folder of the source code package.
+
+    Example:
+    With mycroft running as the user 'bob', if you called
+        resolve_resource_file('snd/beep.wav')
+    it would return either '/home/bob/.mycroft/snd/beep.wav' or
+    '/opt/mycroft/snd/beep.wav' or '.../mycroft/res/snd/beep.wav',
+    where the '...' is replaced by the path where the package has
+    been installed.
+
+    Args:
+        res_name (str): a resource path/name
+    """
+
+    # First look for fully qualified file (e.g. a user setting)
+    if os.path.isfile(res_name):
+        return res_name
+    
+    # Now look for ~/.mycroft/res_name (in user folder)
+    filename = os.path.expanduser("~/.mycroft/"+res_name)
+    if os.path.isfile(filename):
+        return filename
+
+    # Next look for /opt/mycroft/res/res_name
+    filename = os.path.expanduser("/opt/mycroft/"+res_name)
+    if os.path.isfile(filename):
+        return filename
+
+    # Finally look for it in the source package
+    filename = dirname(os.path.abspath(__file__))+"../res/"+res_name
+    filename = os.path.normpath(filename)
+    if os.path.isfile(filename):
+        return filename
+
+    return None  # Resource cannot be resolved
+
+
 def play_wav(uri):
     return subprocess.Popen(["aplay", get_http(uri)])