Comment 1 for bug 1983515

Does this need to be a separate bug from bug 1983514? It'd be difficult to implement without fixing that bug (because we'd fundamentally need to have something like `DistributionSourcePackageCache` to look at anyway) and if that bug were fixed then you could just do `distribution.searchSourcePackages(source_match="")` (possibly with us additionally adding a `DISTINCT` or something to the query to avoid getting duplicate results back).