Don't create log file if not specified

galaxy/api/plugin.py

@@ -318,19 +318,22 @@ class Plugin():
 def _prepare_logging(logger_file):
     root = logging.getLogger()
     root.setLevel(logging.DEBUG)
-    handler = logging.handlers.RotatingFileHandler(
-        logger_file,
-        mode="a",
-        maxBytes=10000000,
-        backupCount=10,
-        encoding="utf-8"
-    )
+    if logger_file:
+        handler = logging.handlers.RotatingFileHandler(
+            logger_file,
+            mode="a",
+            maxBytes=10000000,
+            backupCount=10,
+            encoding="utf-8"
+        )
+    else:
+        handler = logging.StreamHandler()
     formatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s')
     handler.setFormatter(formatter)
     root.addHandler(handler)
 
 def create_and_run_plugin(plugin_class, argv):
-    logger_file = argv[3] if len(argv) >= 4 else "output.log"
+    logger_file = argv[3] if len(argv) >= 4 else None
     _prepare_logging(logger_file)
 
     if len(argv) < 3: