clarify canonical error
clarify canonical error

systemjs/builder,alexisvincent/builder,whitneyit/builder,jrauschenbusch/builder,alexisvincent/builder,systemjs/builder,lookfirst/builder,whitneyit/builder,systemjs/builder,lookfirst/builder,alexisvincent/builder,jrauschenbusch/builder,jrauschenbusch/builder