Retrieve default neural network files from GitHub to pass to Mosaik.

def _get_mosaik_nn_args(out_file):
    """Retrieve default neural network files from GitHub to pass to Mosaik.
    """
    base_nn_url = "https://raw.github.com/wanpinglee/MOSAIK/master/src/networkFile/"
    out = []
    for arg, fname in [("-annse", "2.1.26.se.100.005.ann"),
                       ("-annpe", "2.1.26.pe.100.0065.ann")]:
        arg_fname = os.path.join(os.path.dirname(out_file), fname)
        if not file_exists(arg_fname):
            subprocess.check_call(["wget", "-O", arg_fname, base_nn_url + fname])
        out += [arg, arg_fname]
    return out