Assigning Asset Bundle in Script

I'm trying to assign scenes to asset bundles in an editor script. I searched around online and saw that you can edit the asset bundle of an asset by using:

         Scene scene = EditorSceneManager.NewScene(NewSceneSetup.EmptyScene, NewSceneMode.Additive);
         EditorSceneManager.SaveScene(scene, scenePath);
         EditorSceneManager.CloseScene(scene, true);
         EditorApplication.SaveAssets();

         AssetImporter assetImporter = AssetImporter.GetAtPath(scenePath);
         assetImporter.assetBundleName = chunkName;
         assetImporter.SaveAndReimport();

Unforunately this doesn't appear to work for scenes (it did work for TerrainData), 'assetImporter' becomes null.