fix: Use expect rather than returning error in a theoretically impossible case

iox_catalog/src/interface.rs

@@ -146,11 +146,6 @@ pub enum Error {
 
     #[snafu(display("could not delete namespace: {source}"))]
     CouldNotDeleteNamespace { source: sqlx::Error },
-
-    #[snafu(display("invalid partition template: {source}"))]
-    InvalidPartitionTemplate {
-        source: data_types::partition_template::ValidationError,
-    },
 }
 
 /// A specialized `Error` for Catalog errors

iox_catalog/src/lib.rs

@@ -227,9 +227,10 @@ where
                     table_name,
                     // This table is being created implicitly by this write, so there's no
                     // possibility of a user-supplied partition template here, which is why there's
-                    // a hardcoded `None`.
+                    // a hardcoded `None`. If there is a namespace template, it must be valid because
+                    // validity was checked during its creation, so that's why there's an `expect`.
                     TablePartitionTemplateOverride::try_new(None, namespace_partition_template)
-                        .map_err(|source| Error::InvalidPartitionTemplate { source })?,
+                        .expect("no table partition template; namespace partition template has been validated"),
                     namespace_id,
                 )
                 .await;