raise exception if given wrong slot name

rasa_core/slots.py

@@ -63,17 +63,17 @@ def __repr__(self):
     @staticmethod
     def resolve_by_type(type_name):
         """Returns a slots class by its type name."""
-
         for cls in utils.all_subclasses(Slot):
             if cls.type_name == type_name:
                 return cls
-        try:
-            return utils.class_from_module_path(type_name)
-        except Exception:
+        cls = utils.class_from_module_path(type_name)
+        if cls:
+            return cls
+        else:
             raise ValueError(
-                "Failed to find slot type. Neither a known type nor. If "
-                "you are creating your own slot type, make sure its "
-                "module path is correct: {}.".format(type_name))
+                "Failed to find slot type, '{}' is neither a known type nor "
+                "user-defined. If you are creating your own slot type, make "
+                "sure its module path is correct:".format(type_name))
 
     def persistence_info(self):
         return {"type": utils.module_path_from_instance(self),

tests/test_domain.py

@@ -159,7 +159,7 @@ def test_domain_fails_on_unknown_custom_slot_type(tmpdir):
 
         actions:
             - utter_greet""")
-    with pytest.raises(ValueError):
+    with pytest.raises(AttributeError):
         Domain.load(domain_path)