Triggered by #653

>>> import cpmpy as cp
>>> b = cp.boolvar()
>>> cp.Model(sum(b) == 1).solve()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: '_BoolVarImpl' object is not iterable

cause is in cpmpy/expressions/python_builtins.py: 32a23d85c (wout4 2024-07-18 20:36:53 +0200 153) iterable = tuple(iterable[0]) # Fix generator polling

That line is weird...