The __dict__ attribute of some objects is read-only,
e.g. for type objects.  However, there is a generic
way to still access and modify it (without hacking with
gc.get_referrents(), that is).  This can lead to
obscure crashes.  Attached is an example that shows
a potential "problem" involving putting strange keys
in the __dict__ of a type.

This is probably very minor anyway.  If we wanted to
fix this, we would need a __dict__ descriptor that
looks more cleverly at the object to which it is
applied.

BTW the first person who understand why the attached
program crashes gets a free coffee.