This RFC is asking to:

1. Add the python package dustmaps to the set of third party stack dependencies
2. Add a package called dustmaps_cachedata that holds a cached copy of data so that all users do not need fetch a cached version on their own

Details:
There are at least two packages that use the dustmaps package: faro and pipe_analysis. In the case of faro we would like to add it to lsst_distrib in the near future (that will be an upcoming RFC). Because the unit tests will not run without dustmaps in the dependency tree, will need to add it before we add faro.

The one complication is that the dustmaps package requires data to be cached on disk to work. My proposed solution to this, so that not everyone has to cache the data themselves is to make a data package using git-lfs to store cached data that we can use. Here is a stub of a repository that I plan to add to lsst_distrib at the same time. I plan to only add the sfd maps, but if people think we should cache more than that, let me know.

The dustmaps_cachedata package will set the DUSTMAPS_CONFIG_FNAME to a path within that package containing a config file that points to the data directory in that same package. In order for that to work, I will need to get this this pull request merged, but I have worked with the maintainer before and I don't expect it will be an issue.