Replace use of assert by raise

Change-Id: I6354be35eeed8f32660efd56b956ab5a2841f033
Signed-off-by: garciadeblas <gerardo.garciadeblas@telefonica.com>
diff --git a/osm_nbi/nbi.py b/osm_nbi/nbi.py
index 07716cb..134d565 100644
--- a/osm_nbi/nbi.py
+++ b/osm_nbi/nbi.py
@@ -2630,7 +2630,7 @@
             # elif o == "--log-file":
             #     log_file = a
             else:
-                assert False, "Unhandled option"
+                raise getopt.GetoptError(f"Unhandled option: {o}")
         if config_file:
             if not path.isfile(config_file):
                 print(