revisor - error while reading the file header

[Noriko Mizumoto]

Hi

I have encountered the error of "There was an error while reading the
file header. Please check the header." when opening the file of
revisor/ja.po.
This file has been downloaded from
http://translate.fedoraproject.org/module/revisor.

I see some other languages completed their translation from 'Log of
recent submits' in transifex.
Anyone could you please give me a hand how to fix this error?

Many thanks
noriko