[PATCH 1 of 3 rfc] mpath: split the cpython part from the pure C part

[Maciej Fijalkowski]

>
> This function probably needs to be refactored to not use a PyObject,
> as it looks pretty mpatch-core-algorithm relevant.
>

That's a bit hard, because you can't express it without making an
extra copy of the list (with the associated memory management)