handle exception if border router was not created

modules/preprocessing.py

@@ -14,4 +14,8 @@ def preprocess(definitions, flags):
     """
 
     """ Creating Border router """
-    create_border_router(definitions)
+    try:
+        create_border_router(definitions)
+    except Exception:
+        print("Could not create border router.")
+        raise

modules/routing.py

@@ -51,7 +51,11 @@ def _create_mappings_to_border_router(definitions):
         
 
 def create_border_router(definitions):
-    """ Adds the definition of border router to definitions """
+    """
+    Adds the definition of border router to definitions.
+
+    :param definitions: device definition structure
+    """
 
     # TODO this should be later moved to input check
     if not _are_br_parameters_free: