Patch by Martin Packman.

Patch from Tom Tromey.

Issue #16485: Fix file descriptor not being closed if file header patching fails on closing of aifc file.

The code isn't exactly equivalent because a classmethod would
only make sense inside a chain class, and it would need "cls"
as a first argument, and it would need to return an instance
of "chain" rather than a generator.

The updated example drops the @classmethod decorator so that
it can be used standalone:  list(from_iterable(['abc', 'def']))
This should be communicate what from_iterable does.

This patch also provides a simple way to share tests going forward
between test_int and test_long.