The following code raises MemoryError instead of creating an empty list:

# START
import sys

class CustomIter:
    def __iter__(self):
        return self
    def __next__(self):
        raise StopIteration
    def __length_hint__(self):
        return sys.maxsize

l = list(CustomIter())
#END

That's because this empty iterator has a __length_hint__ that claims it returns a very large number of methods. 

The function listextend in Objects/listobject.c already ignores __length_hint__() when using it would overflow the size of the list, it would IMHO also be better to ignore the length hint when the attempt to resize fails as __length_hint__() is documented as a hint that may be incorrect.