Using Artifacts for test data

Before 1.5, I’d used Artifacts quite successfully to make a large data set (10’s of MB) available for testing. I don’t want to include the test data in the main package because many users will never use it. The Artifact mechanism seemed ideal.

However, recently the scheme has broken. It seems that since Julia is now caching the artifacts on its own server, it no longer looks to the URL specified in the Artifact.toml file for the data. I notice this as errors on Travis

Downloading artifact: rplraw
Exception calling "DownloadFile" with "2" argument(s): "The remote server returned an error: (404) Not Found."
At line:12 char:1
+ $webclient.DownloadFile(" ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : NotSpecified: (:) [], MethodInvocationException
    + FullyQualifiedErrorId : WebException

How do I make the Artifact data available through the cache site? Am I supposed to use PkgBuilder for non-executables?