python: Explicitly use a list

python: Explicitly use a list

On Python 2, the builtin functions filter() returns a list.

On Python 3, it returns an iterator.

Since we want to use those objects in contexts where we need lists, we
need to explicitly turn them into lists.

This makes the code compatible with both Python 2 and Python 3.

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