Normalize path to unicode
    :param path: path
    :return: normalize path

    >>> _(None)
    u''
    >>> _(u("test1"))
    u'test1'
    >>> _("test2")
    u'test2'

def _(path):
    """
    Normalize path to unicode
    :param path: path
    :return: normalize path

    >>> _(None)
    u''
    >>> _(u("test1"))
    u'test1'
    >>> _("test2")
    u'test2'
    """
    if path is None:
        return u("")
    if not PY3:
        if type(path) == unicode:
            return path
        try:
            return _decode_utf8(path)
        except UnicodeDecodeError:
            pass
    return path