Improve pub's pubspec error messages.

sdk/lib/_internal/pub/test/get/git/require_pubspec_name_test.dart

Index: sdk/lib/_internal/pub/test/get/git/require_pubspec_name_test.dart
diff --git a/sdk/lib/_internal/pub/test/get/git/require_pubspec_name_test.dart b/sdk/lib/_internal/pub/test/get/git/require_pubspec_name_test.dart
index 5195b55a3930d0918129b87ca0c7ecd262f52357..530cc82b625f5aaec0ac8773d692625daa648404 100644
--- a/sdk/lib/_internal/pub/test/get/git/require_pubspec_name_test.dart
+++ b/sdk/lib/_internal/pub/test/get/git/require_pubspec_name_test.dart
@@ -4,6 +4,9 @@
 
 library pub_tests;
 
+import 'package:scheduled_test/scheduled_test.dart';
+
+import '../../../lib/src/exit_codes.dart' as exit_codes;
 import '../../descriptor.dart' as d;
 import '../../test_pub.dart';
 
@@ -20,7 +23,7 @@ main() {
 
     d.appDir({"foo": {"git": "../foo.git"}}).create();
 
-    pubGet(error: new RegExp(r'Missing the required "name" field \(e\.g\. '
-        r'"name: foo"\)\.'));
+    pubGet(error: contains('Missing the required "name" field.'),
+        exitCode: exit_codes.DATA);
   });
 }