Fix error message.

Change-Id: I6c4c92aa169de963dd51c3315b6667a5932f0ed1
diff --git a/fs/gitilesfs.go b/fs/gitilesfs.go
index 443f1f7..3557566 100644
--- a/fs/gitilesfs.go
+++ b/fs/gitilesfs.go
@@ -189,7 +189,7 @@
 		if repo != nil {
 			blob, err := repo.LookupBlob(&id)
 			if err != nil {
-				log.Println("LookupBlob: %v", err)
+				log.Printf("LookupBlob: %v", err)
 				return nil, syscall.ESPIPE
 			}
 			defer blob.Free()