def find_package_indexes_in_dir(self, simple_dir):
        """Given a directory that contains simple packages indexes, return
        a sorted list of normalized package names.  This presumes every
        directory within is a simple package index directory."""
        packages = sorted(
            {
                # Filter out all of the "non" normalized names here
                canonicalize_name(x)
                for x in os.listdir(simple_dir)
            }
        )
        # Package indexes must be in directories, so ignore anything else.
        packages = [x for x in packages if os.path.isdir(os.path.join(simple_dir, x))]
        return packages
Given a directory that contains simple packages indexes, return
        a sorted list of normalized package names.  This presumes every
        directory within is a simple package index directory.