[tz] Morocco changes May 27th 2017 instead of May 21th

[Paul Eggert]

Info - avisched.com wrote:
> Morocco is about to switch on May 27th back to UTC from +1.
>
> The current release doesn't reflect that (May 21st).

That's odd, as Morocco World News (the only English-language source I could 
easily find) agrees with tzdb and says the transition is 2017-05-21 at 03:00 
local time. See:

https://www.moroccoworldnews.com/2017/05/216339/morocco-to-switch-back-to-gmt-time-for-ramadan/

What sources are giving May 27 for the transition?