Add debugging for memo parsing

src/ZGoBackend.hs

@@ -376,7 +376,7 @@ zToZGoTx' config pipe (ZcashTx t a aZ bh bt c conf m) = do
         if m_payment zM'
           then upsertPayment pipe (c_dbName config) tx
           else access pipe master (c_dbName config) $ upsertZGoTx "txs" tx
-      Left e -> error "Failed to parse ZGo memo"
+      Left e -> error $ "Failed to parse ZGo memo: " ++ show e
 
 -- |Type to model a price in the ZGo database
 data ZGoPrice =