Correctly handle ErrorResponse after one or more DataRows

Previously, if a query failed with an ErrorResponse after the server had
sent one or more DataRows, stmt.query() incorrectly returned
PgBadResponse.  Fix by handling the error correctly and returning it to
the caller.

src/lib/lib.rs

@@ -1316,6 +1316,10 @@ impl<'stmt> PostgresRows<'stmt> {
                     break;
                 },
                 DataRow { row } => self.data.push_back(row),
+                ErrorResponse { fields } => {
+                    try!(self.stmt.conn.wait_for_ready());
+                    return Err(PgDbError(PostgresDbError::new(fields)));
+                }
                 _ => {
                     self.stmt.conn.conn.borrow_mut().desynchronized = true;
                     return Err(PgBadResponse);

src/test/test.rs

@@ -39,7 +39,8 @@ use postgres::error::{PgConnectDbError,
                       QueryCanceled,
                       UndefinedTable,
                       InvalidCatalogName,
-                      PgWrongTransaction};
+                      PgWrongTransaction,
+                      CardinalityViolation};
 use postgres::types::{ToSql, FromSql, PgInt4, PgVarchar};
 use postgres::types::array::{ArrayBase};
 use postgres::types::range::{Range, Inclusive, Exclusive, RangeBound};
@@ -361,6 +362,23 @@ fn test_query() {
     assert_eq!(vec![1i64, 2], result.map(|row| row.get(0u)).collect());
 }
 
+#[test]
+fn test_error_after_datarow() {
+    let conn = or_fail!(PostgresConnection::connect("postgres://postgres@localhost", &NoSsl));
+    let stmt = or_fail!(conn.prepare("
+SELECT
+    (SELECT generate_series(1, ss.i))
+FROM (SELECT gs.i
+      FROM generate_series(1, 2) gs(i)
+      ORDER BY gs.i
+      LIMIT 2) ss"));
+    match stmt.query([]) {
+        Err(PgDbError(PostgresDbError { code: CardinalityViolation, .. })) => {}
+        Err(err) => fail!("Unexpected error {}", err),
+        Ok(_) => fail!("Expected failure"),
+    }
+}
+
 #[test]
 fn test_result_finish() {
     let conn = or_fail!(PostgresConnection::connect("postgres://postgres@localhost", &NoSsl));