Fixed string conversion.

modules/core/engine.py

@@ -534,7 +534,7 @@ class SoundSystem():
         while not self.stream_is_ready(entry.channel, entry.source):
             self.logger.info("Loading Stream ...")
             if retries >= max_retries:
-                raise LoadSourceException("Could not connect to stream while waiting for %s seconds!" % retries*retry_delay)
+                raise LoadSourceException("Could not connect to stream while waiting for %s seconds!" % str(retries*retry_delay))
             time.sleep(retry_delay)
             retries += 1