Revert "Use native async/await support in pub."

sdk/lib/_internal/pub_generated/test/validator/utils.dart

Index: sdk/lib/_internal/pub_generated/test/validator/utils.dart
diff --git a/sdk/lib/_internal/pub/test/validator/utils.dart b/sdk/lib/_internal/pub_generated/test/validator/utils.dart
similarity index 87%
copy from sdk/lib/_internal/pub/test/validator/utils.dart
copy to sdk/lib/_internal/pub_generated/test/validator/utils.dart
index 64a6b47d956e852302675676e05bcccc5154c703..def5bb9878d61a6610176d2ce59315043f02cf5b 100644
--- a/sdk/lib/_internal/pub/test/validator/utils.dart
+++ b/sdk/lib/_internal/pub_generated/test/validator/utils.dart
@@ -13,11 +13,13 @@ void expectNoValidationError(ValidatorCreator fn) {
 }
 
 void expectValidationError(ValidatorCreator fn) {
-  expect(schedulePackageValidation(fn),
+  expect(
+      schedulePackageValidation(fn),
       completion(pairOf(isNot(isEmpty), anything)));
 }
 
 void expectValidationWarning(ValidatorCreator fn) {
-  expect(schedulePackageValidation(fn),
+  expect(
+      schedulePackageValidation(fn),
       completion(pairOf(isEmpty, isNot(isEmpty))));
 }