I should be working by now.

src/util.rs

@@ -3,6 +3,7 @@ use rusqlite::{Params, Row, Transaction};
 #[derive(Debug)]
 pub enum Error {
     SqlError(rusqlite::Error),
+    DoubleBooking(String),
     InvalidDrawer(String),
     InvalidAmount(String),
     InvalidPayee(String),