def _add_proposed():
    """Add the PROPOSED_POCKET as /etc/apt/source.list.d/proposed.list

    Uses get_distrib_codename to determine the correct stanza for
    the deb line.

    For intel architecutres PROPOSED_POCKET is used for the release, but for
    other architectures PROPOSED_PORTS_POCKET is used for the release.
    """
    release = get_distrib_codename()
    arch = platform.machine()
    if arch not in six.iterkeys(ARCH_TO_PROPOSED_POCKET):
        raise SourceConfigError("Arch {} not supported for (distro-)proposed"
                                .format(arch))
    with open('/etc/apt/sources.list.d/proposed.list', 'w') as apt:
        apt.write(ARCH_TO_PROPOSED_POCKET[arch].format(release))