Build API: Standardize return codes.

BUG=chromium:963605
TEST=run_tests

Change-Id: If05654fe56e24425da1b89b8d516cc7ba6bebd3f
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/1615507
Tested-by: Alex Klein <saklein@chromium.org>
Tested-by: David Burger <dburger@chromium.org>
Commit-Queue: Alex Klein <saklein@chromium.org>
Reviewed-by: David Burger <dburger@chromium.org>
Reviewed-by: Evan Hernandez <evanhernandez@chromium.org>
diff --git a/api/controller/sysroot_unittest.py b/api/controller/sysroot_unittest.py
index 2598130..35c0f55 100644
--- a/api/controller/sysroot_unittest.py
+++ b/api/controller/sysroot_unittest.py
@@ -9,6 +9,7 @@
 
 import os
 
+from chromite.api import controller
 from chromite.api.controller import sysroot as sysroot_controller
 from chromite.api.gen.chromite.api import sysroot_pb2
 from chromite.lib import build_target_util
@@ -181,7 +182,7 @@
     self.PatchObject(sysroot_service, 'InstallToolchain', side_effect=err)
 
     rc = sysroot_controller.InstallToolchain(in_proto, out_proto)
-    self.assertTrue(rc)
+    self.assertEqual(controller.RETURN_CODE_UNSUCCESSFUL_RESPONSE_AVAILABLE, rc)
     self.assertTrue(out_proto.failed_packages)
     for package in out_proto.failed_packages:
       cat_pkg = (package.category, package.package_name)