private static IEnumerable<FeedUri> GetSitePackagePaths(FeedUri interfaceUri)
{
var sitePackageDirs = Locations.GetLoadDataPaths("0install.net", isFile: false, resource: interfaceUri.EscapeComponent().Prepend("site-packages"));
var subDirectories = sitePackageDirs.SelectMany(x => new DirectoryInfo(x).GetDirectories());
return
from dir in subDirectories
let path = Path.Combine(dir.FullName, "0install" + Path.DirectorySeparatorChar + "feed.xml")
where File.Exists(path)
select new FeedUri(path);
}