refactor/tts_mode

allow audio service to load even if there are no audio backend plugins

We always want the voice assistant to be able to speak, even if skills can not play music

mycroft/audio/__main__.py

@@ -34,7 +34,7 @@ def on_ready():
 
 
 def on_error(e='Unknown'):
-    LOG.error('Audio service failed to launch ({}).'.format(repr(e)))
+    LOG.error(f'Audio service failed to launch ({e}).')
 
 
 def on_stopping():
@@ -64,13 +64,17 @@ def main(ready_hook=on_ready, error_hook=on_error, stopping_hook=on_stopping):
     except Exception as e:
         status.set_error(e)
     else:
-        if audio.wait_for_load() and len(audio.service) > 0:
-            # If at least one service exists, report ready
+        if audio.wait_for_load():
+            if len(audio.service) == 0:
+                LOG.warning('No audio backends loaded! Audio playback is not available')
+                LOG.info("Running audio service in TTS only mode")
+        # If at least TTS exists, report ready
+        if speech.tts:
             status.set_ready()
             wait_for_exit_signal()
             status.set_stopping()
         else:
-            status.set_error('No audio services loaded')
+            status.set_error('No TTS loaded')
 
         speech.shutdown()
         audio.shutdown()