Store the async-await compiled pub code directly in the repo.

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

+import 'package:scheduled_test/scheduled_test.dart';
+import '../../lib/src/exit_codes.dart' as exit_codes;
+import '../test_pub.dart';
+void pubBuildAndServeShouldFail(String description, {List<String> args,
+    String error, String buildError, String serveError, int exitCode}) {
+  if (error != null) {
+    assert(buildError == null);
+    buildError = error;
+    assert(serveError == null);
+    serveError = error;
+  }
+  var buildExpectation = buildError;
+  var serveExpectation = serveError;
+  if (exitCode == exit_codes.USAGE) {
+    buildExpectation =
+        allOf(startsWith(buildExpectation), contains("Usage: pub build"));
+    serveExpectation =
+        allOf(startsWith(serveExpectation), contains("Usage: pub serve"));
+  }
+  integration("build fails $description", () {
+    schedulePub(
+        args: ["build"]..addAll(args),
+        error: buildExpectation,
+        exitCode: exitCode);
+  });
+  integration("build --format json fails $description", () {
+    schedulePub(args: ["build", "--format", "json"]..addAll(args), outputJson: {
+      "error": buildError
+    }, exitCode: exitCode);
+  });
+  integration("serve fails $description", () {
+    schedulePub(
+        args: ["serve"]..addAll(args),
+        error: serveExpectation,
+        exitCode: exitCode);
+  });
+}