Change package scheduled_test to throw TestFailures rather than strings.

pkg/scheduled_test/test/descriptor/file_test.dart

Index: pkg/scheduled_test/test/descriptor/file_test.dart
diff --git a/pkg/scheduled_test/test/descriptor/file_test.dart b/pkg/scheduled_test/test/descriptor/file_test.dart
index e22a9929fab4870831141dbb64bf5b31f490e954..e458a24db406bee753974e22cd673324404ae35c 100644
--- a/pkg/scheduled_test/test/descriptor/file_test.dart
+++ b/pkg/scheduled_test/test/descriptor/file_test.dart
@@ -100,7 +100,8 @@ void main() {
     test('test 2', () {
       expect(errors, everyElement(new isInstanceOf<ScheduleError>()));
       expect(errors.length, equals(1));
-      expect(errors.first.error,
+      expect(errors.first.error, new isInstanceOf<TestFailure>());
+      expect(errors.first.error.message,
           matches(r"^File not found: '[^']+[\\/]name\.txt'\.$"));
     });
   }, passing: ['test 2']);
@@ -165,10 +166,10 @@ void main() {
     });
 
     test('test 2', () {
-      expect(errors, everyElement(new isInstanceOf<ScheduleError>()));
-      expect(errors.map((e) => e.error), equals([
-        "File 'name.bin' didn't contain the expected binary data."
-      ]), verbose: true);
+      expect(errors.single, new isInstanceOf<ScheduleError>());
+      expect(errors.single.error, new isInstanceOf<TestFailure>());
+      expect(errors.single.error.message, equals(
+          "File 'name.bin' didn't contain the expected binary data."));
     });
   }, passing: ['test 2']);