can't checkout ghc 8.6 branch correctly -- something wrong with transformers mirror repo?

[Carter Schonwald]

Hey everyone, whats wrong with the 8.6 branch?

when i do a fresh clone, i wind up with this error :
$
git submodule update  --init --recursive
error: Server does not allow request for unadvertised object
def8c55d0c47c1c40de985d83f052f3659b40cfd
Fetched in submodule path 'libraries/transformers', but it did not contain
def8c55d0c47c1c40de985d83f052f3659b40cfd. Direct fetching of that commit
failed.
14:17:43 ~/D/r/ghc-8.6.5-series (ghc-8.6|✚6) $
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.haskell.org/pipermail/ghc-devs/attachments/20190726/d4f3691e/attachment.html>