Fix various deprecated code (via lib2to3).

def fix_2to3(source,
             aggressive=True, select=None, ignore=None, filename='',
             where='global', verbose=False):
    """Fix various deprecated code (via lib2to3)."""
    if not aggressive:
        return source

    select = select or []
    ignore = ignore or []

    return refactor(source,
                    code_to_2to3(select=select,
                                 ignore=ignore,
                                 where=where,
                                 verbose=verbose),
                    filename=filename)