"yield from ..." doesn't create a generator

[ytyt_lead]

def demo_generator():
    data = [1, 2, 3, 4, 5]

    yield from data


gen = demo_generator()
print(next(gen))
print(next(gen))

Expected behaviour:
1
2

Real behaviour:
<TypeError: 'NoneType' object is not an iterator>

[stu]

Closing since this works on the master branch - fixed in #1241