Display warning message in BundleCheck hook

The post-checkout `BundleCheck` hook would return a warning status but
not display a message if the dependencies were out of date.

Change it to actually display a warning message.

Change-Id: I064b5777108967d3e571e46e48d31dd64282d197
Reviewed-on: http://gerrit.causes.com/36485
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Shane da Silva <shane@causes.com>