fix install checks in flavors devicelab tests (#133719)

Fixes #133713

dev/devicelab/bin/tasks/flavors_test.dart

@@ -13,8 +13,10 @@ Future<void> main() async {
   await task(() async {
     await createFlavorsTest().call();
     await createIntegrationTestFlavorsTest().call();
-    // test install and uninstall of flavors app
-    await inDirectory('${flutterDirectory.path}/dev/integration_tests/flavors', () async {
+
+    final TaskResult installTestsResult = await inDirectory(
+      '${flutterDirectory.path}/dev/integration_tests/flavors',
+      () async {
         await flutter(
           'install',
           options: <String>['--debug', '--flavor', 'paid'],
@@ -23,6 +25,7 @@ Future<void> main() async {
           'install',
           options: <String>['--debug', '--flavor', 'paid', '--uninstall-only'],
         );
+
         final StringBuffer stderr = StringBuffer();
         await evalFlutter(
           'install',
@@ -32,12 +35,15 @@ Future<void> main() async {
         );
 
         final String stderrString = stderr.toString();
-      if (!stderrString.contains('The Xcode project defines schemes: free, paid')) {
+        if (!stderrString.contains('"build/app/outputs/flutter-apk/app-bogus-release.apk" does not exist.')) {
           print(stderrString);
           return TaskResult.failure('Should not succeed with bogus flavor');
         }
-    });
 
         return TaskResult.success(null);
+      },
+    );
+
+    return installTestsResult;
   });
 }

dev/devicelab/bin/tasks/flavors_test_ios.dart

@@ -14,7 +14,9 @@ Future<void> main() async {
     await createFlavorsTest().call();
     await createIntegrationTestFlavorsTest().call();
     // test install and uninstall of flavors app
-    await inDirectory('${flutterDirectory.path}/dev/integration_tests/flavors', () async {
+    final TaskResult installTestsResult = await inDirectory(
+      '${flutterDirectory.path}/dev/integration_tests/flavors',
+      () async {
         await flutter(
           'install',
           options: <String>['--flavor', 'paid'],
@@ -32,12 +34,15 @@ Future<void> main() async {
         );
 
         final String stderrString = stderr.toString();
-      if (!stderrString.contains('install failed, bogus flavor not found')) {
+        if (!stderrString.contains('The Xcode project defines schemes: free, paid')) {
           print(stderrString);
           return TaskResult.failure('Should not succeed with bogus flavor');
         }
-    });
 
         return TaskResult.success(null);
+      },
+    );
+
+    return installTestsResult;
   });
 }

dev/devicelab/bin/tasks/flavors_test_macos.dart

@@ -14,7 +14,9 @@ Future<void> main() async {
     await createFlavorsTest().call();
     await createIntegrationTestFlavorsTest().call();
 
-    await inDirectory('${flutterDirectory.path}/dev/integration_tests/flavors', () async {
+    final TaskResult installTestsResult = await inDirectory(
+      '${flutterDirectory.path}/dev/integration_tests/flavors',
+      () async {
         final StringBuffer stderr = StringBuffer();
 
         await evalFlutter(
@@ -32,8 +34,11 @@ Future<void> main() async {
           print(stderrString);
           return TaskResult.failure('Installing a macOS app on macOS should no-op');
         }
-    });
 
         return TaskResult.success(null);
+      },
+    );
+
+    return installTestsResult;
   });
 }