Use helper methods for running pub.

sdk/lib/_internal/pub/test/install/hosted/install_test.dart

Index: sdk/lib/_internal/pub/test/install/hosted/install_test.dart
diff --git a/sdk/lib/_internal/pub/test/install/hosted/install_test.dart b/sdk/lib/_internal/pub/test/install/hosted/install_test.dart
index 5db55532ddc4920e33612f727f6f1335456ad0f6..375860af0a263f0c30aa8902871c71c16040dc61 100644
--- a/sdk/lib/_internal/pub/test/install/hosted/install_test.dart
+++ b/sdk/lib/_internal/pub/test/install/hosted/install_test.dart
@@ -16,8 +16,7 @@ main() {
 
     d.appDir([dependencyMap("foo", "1.2.3")]).create();
 
-    schedulePub(args: ['install'],
-        output: new RegExp("Dependencies installed!\$"));
+    pubInstall();
 
     d.cacheDir({"foo": "1.2.3"}).validate();
     d.packagesDir({"foo": "1.2.3"}).validate();
@@ -28,9 +27,7 @@ main() {
 
     d.appDir([dependencyMap("bad name!", "1.2.3")]).create();
 
-    schedulePub(args: ['install'],
-        error: new RegExp('Could not find package "bad name!" at '
-                          'http://localhost:'),
-        exitCode: 1);
+    pubInstall(error: new RegExp(
+        r'Could not find package "bad name!" at http://localhost:\d+\.$'));
   });
 }