def convert_lists(varmap, listnames=('classifiers', 'requires', 'provides',
    'obsoletes')):
    """Convert long strings to lists of strings.
    
    Allows variable names in ``listnames`` to be specified as
    long strings instead of lists, for easier typing. The
    ``license_map`` and ``devstatus_trove`` strings below give
    examples of the kind of long strings that can be used.
    """
    listnames = varmap.get('listnames', listnames)
    for listname in listnames:
        try:
            var = varmap[listname]
        except KeyError:
            pass
        else:
            if isinstance(var, str):
                varmap[listname] = var.strip().splitlines()
