Raise exception

Author: ocelotl

opentelemetry-sdk/src/opentelemetry/sdk/_metrics/aggregation.py

@@ -120,7 +120,8 @@ def _create_aggregation(self, instrument: Instrument) -> _Aggregation:
         if isinstance(instrument, ObservableGauge):
             return _LastValueAggregation()
 
-        return None
+        else:
+            raise Exception("Invalid aggregation type found")
 
 
 class _SumAggregation(_Aggregation[Sum]):