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.py b/api/controller/sysroot.py
index 04aa31e..518bac4 100644
--- a/api/controller/sysroot.py
+++ b/api/controller/sysroot.py
@@ -7,6 +7,7 @@
 
 from __future__ import print_function
 
+from chromite.api import controller
 from chromite.api.controller import controller_util
 from chromite.lib import build_target_util
 from chromite.lib import cros_build_lib
@@ -15,9 +16,6 @@
 
 _ACCEPTED_LICENSES = '@CHROMEOS'
 
-# Return codes.
-RC_ERROR = 1
-
 
 def Create(input_proto, output_proto):
   """Create or replace a sysroot."""
@@ -71,7 +69,7 @@
       package_info = output_proto.failed_packages.add()
       controller_util.CPVToPackageInfo(package, package_info)
 
-    return RC_ERROR
+    return controller.RETURN_CODE_UNSUCCESSFUL_RESPONSE_AVAILABLE
 
 
 def InstallPackages(input_proto, output_proto):
@@ -105,4 +103,4 @@
       package_info = output_proto.failed_packages.add()
       controller_util.CPVToPackageInfo(package, package_info)
 
-    return RC_ERROR
+    return controller.RETURN_CODE_UNSUCCESSFUL_RESPONSE_AVAILABLE