only output exception in verbose mode

shadowsocks/local.py

@@ -68,8 +68,9 @@ def main():
         loop.run()
     except (KeyboardInterrupt, IOError, OSError) as e:
         logging.error(e)
-        import traceback
+        if config['verbose']:
-        traceback.print_exc()
+            import traceback
+            traceback.print_exc()
         os._exit(1)
 
 if __name__ == '__main__':

shadowsocks/server.py

@@ -79,8 +79,9 @@ def main():
             loop.run()
         except (KeyboardInterrupt, IOError, OSError) as e:
             logging.error(e)
-            import traceback
+            if config['verbose']:
-            traceback.print_exc()
+                import traceback
+                traceback.print_exc()
             os._exit(1)
 
     if int(config['workers']) > 1: