Remove err.response from SavedObjects fetch errors

src/core/public/saved_objects/saved_objects_client.ts

@@ -423,11 +423,15 @@ export class SavedObjectsClient {
   /**
    * To ensure we don't break backwards compatibility, savedObjectsFetch keeps
    * the old kfetch error format of `{res: {status: number}}` whereas `http.fetch`
-   * uses `{response: {status: number}}`
+   * uses `{response: {status: number}}`.
+   *
+   * TODO: Introduce error helper functions to make it easier to change
+   * the internal shape of errors.
    */
   private savedObjectsFetch(path: string, { method, query, body }: HttpFetchOptions) {
     return this.http.fetch(path, { method, query, body }).catch(err => {
       const kfetchError = Object.assign(err, { res: err.response });
+      delete kfetchError.response;
       return Promise.reject(kfetchError);
     });
   }