Scripts: Fix return value.

src/Scripts/Hello.py

@@ -31,4 +31,4 @@ class ScriptHello(AScript):
 
     def run(self):
         logger.info("Hello from Pamhyr2 script !")
-        return True
+        return 0

src/pamhyr.py

@@ -90,7 +90,7 @@ def main():
 
             application = scripts[script](app, conf, sys.argv)
             ret = application.run()
-            if not ret:
+            if ret != 0:
                 application.usage()
     else:
         # No args, run Pamhyr2 interface