Fix missing variable error.
Fix missing variable error.

It would cause an exception when it should have been a warning.

TBR=vadimsh@chromium.org
BUG=

Review URL: https://codereview.appspot.com/63190043

luci/luci-py,pombreda/swarming,madecoste/swarming,luci/luci-py,madecoste/swarming,pombreda/swarming,luci/luci-py,madecoste/swarming,pombreda/swarming,luci/luci-py,madecoste/swarming,pombreda/swarming