avoid stack print when running --help

diff --git a/system/TestMain.py b/system/TestMain.py
index 32ea7a0..5e7d8f8 100755 (executable)
--- a/system/TestMain.py
+++ b/system/TestMain.py
@@ -214,6 +214,8 @@ steps refer to a method in TestPlc or to a step_* module"""%(TestMain.default_bu
                 return 0
             else:
                 return 1 
+        except SystemExit:
+            raise
         except:
             traceback.print_exc()
             return 2