--- a/connectors/__init__.py	Wed Dec 05 14:05:35 2018 +0100
+++ b/connectors/__init__.py	Mon Dec 10 11:22:43 2018 +0100
@@ -86,6 +86,9 @@
     # first call to import the module, 
     # then call with parameters to create the class
     connector_specific_class = connectors[scheme]()(uri, confnodesroot)
+    
+    if connector_specific_class is None:
+        return None
 
     # new class inheriting from generic and specific connector base classes
     return ClassType(_scheme + "_connector",