Bugfix. Reference to a constant.

BUG=chromium:257241
TEST=common_util_unittest.py

Change-Id: I4a209df2431b0b4fcef15ebc6ff050fe9c2fe8bb
Reviewed-on: https://gerrit.chromium.org/gerrit/61293
Reviewed-by: Chris Sosa <sosa@chromium.org>
Commit-Queue: Joy Chen <joychen@chromium.org>
Reviewed-by: Joy Chen <joychen@chromium.org>
Tested-by: Joy Chen <joychen@chromium.org>
diff --git a/common_util_unittest.py b/common_util_unittest.py
index a19fcc5..a983bde 100755
--- a/common_util_unittest.py
+++ b/common_util_unittest.py
@@ -15,6 +15,7 @@
 
 import build_artifact
 import common_util
+import devserver_constants
 
 
 # Fake Dev Server Layout:
@@ -46,7 +47,7 @@
           build_path, build_artifact.STATEFUL_UPDATE_FILE), 'w') as f:
           f.write('STATEFUL_UPDATE_FILE')
         with open(os.path.join(
-          build_path, build_artifact.ROOT_UPDATE_FILE), 'w') as f:
+          build_path, devserver_constants.ROOT_UPDATE_FILE), 'w') as f:
           f.write('ROOT_UPDATE_FILE')
 
   def tearDown(self):