channeldb+contractcourt: add additional logging around co-op channel closes

channeldb/db.go

@@ -493,8 +493,8 @@ func (d *DB) MarkChanFullyClosed(chanPoint *wire.OutPoint) error {
 
 		chanSummaryBytes := closedChanBucket.Get(chanID)
 		if chanSummaryBytes == nil {
-			return fmt.Errorf("no closed channel by that chanID " +
-				"found")
+			return fmt.Errorf("no closed channel for "+
+				"chan_point=%v found", chanPoint)
 		}
 
 		chanSummaryReader := bytes.NewReader(chanSummaryBytes)