Fix for new printf

Author: sfackler

src/postgres/lib.rs

@@ -794,7 +794,7 @@ impl<'self> NormalPostgresStatement<'self> {
         let mut formats = ~[];
         let mut values = ~[];
         assert!(self.param_types.len() == params.len(),
-                "Expected %u parameters but found %u",
+                "Expected {} parameters but found {}",
                 self.param_types.len(), params.len());
         for (&param, &ty) in params.iter().zip(self.param_types.iter()) {
             let (format, value) = param.to_sql(ty);