Fix typo in release script

Change-Id: I0b9b8a9dc14a741cf6e24977edf6e413acdde524
diff --git a/tools/r8_release.py b/tools/r8_release.py
index 39f60c0..60f48de 100755
--- a/tools/r8_release.py
+++ b/tools/r8_release.py
@@ -289,7 +289,7 @@
 def prepare_google3(args):
   assert args.version
   # Check if an existing client exists.
-  if not options.use_existing_work_branch:
+  if not args.use_existing_work_branch:
     if ':update-r8:' in subprocess.check_output('g4 myclients', shell=True):
       print "Remove the existing 'update-r8' client before continuing."
       sys.exit(1)