def package(pkg_name, update=False):
    """
    Require a Portage package to be installed.

    Example::

        from fabtools import require

        require.portage.package('foo')
    """
    if not is_installed(pkg_name):
        install(pkg_name, update)
def packages(pkg_list, update=False):
    """
    Require several Portage packages to be installed.

    Example::

        from fabtools import require

        require.portage.packages([
            'foo',
            'bar',
            'baz',
        ])
    """
    pkg_list = [pkg for pkg in pkg_list if not is_installed(pkg)]
    if pkg_list:
        install(pkg_list, update)