python: Better use iterators

python: Better use iterators

In Python 2, iterators had a .next() method.

In Python 3, instead they have a .__next__() method, which is
automatically called by the next() builtin.

In addition, it is better to use the iter() builtin to create an
iterator, rather than calling its __iter__() method.

These were also introduced in Python 2.6, so using it makes the script
compatible with Python 2 and 3.

Signed-off-by: Mathieu Bridon <bochecha@daitauha.fr>
Reviewed-by: Eric Engestrom <eric.engestrom@intel.com>
Reviewed-by: Dylan Baker <dylan@pnwbakers.com>