Remove Expect from core library.

tests/language/exception_test.dart

Index: tests/language/exception_test.dart
diff --git a/tests/language/exception_test.dart b/tests/language/exception_test.dart
index 0876c5c2327950090f6f9e7625c76fdf0a0d7331..2cdab5e0977fa05a1a11a5fc48acd56c4cfd867e 100644
--- a/tests/language/exception_test.dart
+++ b/tests/language/exception_test.dart
@@ -1,6 +1,9 @@
 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
+
+import "package:expect/expect.dart";
+
 class ExceptionTest {
   static testMain() {
     int i = 0;