npbackend: avoid having METH_KEYWORDS alone
npbackend: avoid having METH_KEYWORDS alone

Python3 has a problem with METH_KEYWORDS standing alone: https://bugs.python.org/issue11587

bh107/bohrium,madsbk/bohrium,bh107/bohrium,madsbk/bohrium,bh107/bohrium,madsbk/bohrium,bh107/bohrium,madsbk/bohrium