'Return the indices associated with an alias.
If we are reindexing, there should be two indices returned.'

@classmethod
def get_indices(cls, alias):

    try:
        reindex = cls.objects.get(alias=alias)
        return [idx for idx in (reindex.new_index, reindex.old_index) if (idx is not None)]
    except Reindexing.DoesNotExist:
        return [alias]
