exit witha n error when bundler req isn't satisfied

Change-Id: I2d2c60e7009528964abc5ce2196e929b633a26d4
Reviewed-on: https://gerrit.instructure.com/28493
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: Cody Cutrer <cody@instructure.com>
Product-Review: Cody Cutrer <cody@instructure.com>
Reviewed-by: Cody Cutrer <cody@instructure.com>