add a message to L3 lenght assertion

gso/workflows/l3_core_service/shared.py

@@ -15,7 +15,9 @@ L3_PRODUCT_NAMES = [
     ProductName.COPERNICUS,
 ]
 L3_CORE_SERVICE_PRODUCT_TYPES = [GeantIP.__name__, IAS.__name__, LHCOne.__name__, Copernicus.__name__]
-assert len(L3_PRODUCT_NAMES) == len(L3_CORE_SERVICE_PRODUCT_TYPES)  # noqa: S101
+assert len(L3_PRODUCT_NAMES) == len(  # noqa: S101
+    L3_CORE_SERVICE_PRODUCT_TYPES
+), "The number of L3 product names does not match the number of L3 core service product types."
 
 L3ProductNameType = Literal[ProductName.IAS, ProductName.LHCONE, ProductName.COPERNICUS, ProductName.GEANT_IP]