Don't expect single quote around IsolateSpawnException message in tests.

sdk/lib/_internal/pub_generated/test/transformer/fails_to_load_a_transform_with_an_import_error_test.dart

Index: sdk/lib/_internal/pub_generated/test/transformer/fails_to_load_a_transform_with_an_import_error_test.dart
diff --git a/sdk/lib/_internal/pub_generated/test/transformer/fails_to_load_a_transform_with_an_import_error_test.dart b/sdk/lib/_internal/pub_generated/test/transformer/fails_to_load_a_transform_with_an_import_error_test.dart
index 948fb571ebc99494757b1a38030fd9561f4c6c5a..0ce85de818b9927d22dc8e98f6542ec9840f96eb 100644
--- a/sdk/lib/_internal/pub_generated/test/transformer/fails_to_load_a_transform_with_an_import_error_test.dart
+++ b/sdk/lib/_internal/pub_generated/test/transformer/fails_to_load_a_transform_with_an_import_error_test.dart
@@ -19,7 +19,7 @@ main() {
                         [d.file("transformer.dart", "import 'does/not/exist.dart';")])])]).create();
       createLockFile('myapp', pkg: ['barback']);
       var pub = startPubServe();
-      pub.stderr.expect("'Unhandled exception:");
+      pub.stderr.expect("Unhandled exception:");
       pub.stderr.expect(startsWith("Uncaught Error: Failure getting "));
       pub.shouldExit(1);
     });