Fix issue writing phonemes to disk (#1720)

Change Mimic.get_tts() to return phonemes as string instead of bytes

mycroft/tts/__init__.py

@@ -352,7 +352,7 @@ class TTS(object):
             with open(pho_file, "w") as cachefile:
                 cachefile.write(phonemes)
         except Exception:
-            LOG.exception("Failed to write %s to cache" % pho_file)
+            LOG.exception("Failed to write {} to cache".format(pho_file))
             pass
 
     def load_phonemes(self, key):

mycroft/tts/mimic_tts.py

@@ -143,7 +143,7 @@ class Mimic(TTS):
         #  Generate WAV and phonemes
         phonemes = subprocess.check_output(self.args + ['-o', wav_file,
                                                         '-t', sentence])
-        return wav_file, phonemes
+        return wav_file, phonemes.decode()
 
     def visime(self, output):
         visimes = []