When trying to update a record, this error will occur when the entity has already been deleted in Salesforce.
E2120 - ECE_SForceDataError: We got an error back from SalesForce when trying to update or insert data in SalesForce: Error returned from SFDC on upsert: [message: entity is deleted , statusCode: ENTITY_IS_DELETED ].
If you are looking to Delete the record, then the job is already done for you. If you were looking to Update the record, then you would need to create it again by Inserting it, as the previously referenced record no longer exists.