chore: replace print with logging and make robot conditional

All print statements in the main program, and components used by the main program, have been replaced with appropriate logging statements. The connection to the robot now only gets made when it's possible, otherwise only the microphone will be run.

ref: N25B-119

main.py

@@ -1,4 +1,7 @@
-import qi
+import sys
+import logging
+logging.
+
 import zmq
 
 from src.audio_streaming import AudioStreaming
@@ -19,23 +22,38 @@ def listen_for_messages(session):
     poller = zmq.Poller()
     poller.register(socket, zmq.POLLIN)
 
-    print("Listening for messages")
+    logging.info("Listening for messages")
     while not state.exit_event.is_set():
         if not poller.poll(200): continue  # At most 200 ms delay after CTRL+C
         # We now know there's a message waiting for us
         message = socket.recv_string()
-        print("Received message: {}".format(message))
+        logging.debug("Received message: {}".format(message))
 
         if session: say(session, message)
 
 
-def main():
+def get_session():
+    if "--qi-url" not in sys.argv:
+        logging.info("No Qi URL argument given. Running in stand-alone mode.")
+        return None
+
+    try:
+        import qi
+    except ImportError:
+        logging.info("Unable to import qi. Running in stand-alone mode.")
+        return None
+
     try:
         app = qi.Application()
         app.start()
-        session = app.session
+        return app.session
     except RuntimeError:
-        session = None
+        logging.info("Unable to connect to the robot. Running in stand-alone mode.")
+        return None
+
+
+def main():
+    session = get_session()
 
     audio_streamer = AudioStreaming()
     audio_streamer.run()