Glyphset is unordered

[sovichet]

It looks like python set() makes the provided glyphset unordered.

Here is the result when I ran the ufomerge.

[simoncozens]

Is this with the latest version? Because we don't use set data types for anything which needs order preservation; and although the routine which assigns public.glyphOrder is called merge_set, it doesn't use sets but order-preserving dictionaries.

Can you make a small reproducer?