At least, by the Brightway2 exporter, which calls in order: - [link_internal](https://github.com/IndEcol/wurst/blob/master/wurst/brightway/write_database.py#L49) - [reference_product](https://github.com/IndEcol/wurst/blob/master/wurst/linking.py#L9) which [raises an error](https://github.com/IndEcol/wurst/blob/master/wurst/searching.py#L86).
At least, by the Brightway2 exporter, which calls in order:
which raises an error.