Make _paused state an event

This removes the need for a busy waiting  while / sleep check, instead
uses the Event.wait() to wait until playback is resumed.

mycroft/tts/tts.py

@@ -17,7 +17,7 @@
 import random
 import re
 from abc import ABCMeta, abstractmethod
-from threading import Thread
+from threading import Event, Thread
 from time import time, sleep
 from warnings import warn
 
@@ -54,7 +54,10 @@ class PlaybackThread(Thread):
     def __init__(self, queue):
         super(PlaybackThread, self).__init__()
         self.queue = queue
-        self._paused = False
+
+        self._free_to_play = Event()
+        self._free_to_play.set()
+
         self._terminated = False
         self._processing_queue = False
         self.enclosure = None
@@ -94,8 +97,7 @@ def run(self):
         listening.
         """
         while not self._terminated:
-            while self._paused:
-                sleep(0.2)
+            self._free_to_play.wait()
             try:
                 (snd_type, data,
                  visemes, ident, listen) = self.queue.get(timeout=2)
@@ -116,7 +118,7 @@ def run(self):
 
                     if self.p:
                         while self.p.poll() is None:
-                            if self._paused:
+                            if not self._free_to_play.is_set():
                                 self.p.terminate()
                                 break
                             sleep(0.1)
@@ -157,12 +159,12 @@ def blink(self, rate=1.0):
             self.enclosure.eyes_blink("b")
 
     def pause(self):
-        """pause thread"""
-        self._paused = True
+        """Signal that the thread is no longer free to play."""
+        self._free_to_play.clear()
 
     def resume(self):
-        """resume thread"""
-        self._paused = False
+        """Signal that the thred is now free to play."""
+        self._free_to_play.set()
 
     def stop(self):
         """Stop thread"""