Resolve a relative module name to an absolute one.

def resolve_name(name, package):
    """Resolve a relative module name to an absolute one."""
    if not name.startswith('.'):
        return name
    elif not package:
        raise ValueError('{!r} is not a relative name '
                         '(no leading dot)'.format(name))
    level = 0
    for character in name:
        if character != '.':
            break
        level += 1
    return _resolve_name(name[level:], package, level)