Noticed this in xwiki.cfg, diff between 8.4.4 and 9.0:
102c105
< # xwiki.store.migration.manager.hint=hibernate
---
#
xwiki.store.migration.manager.hint=hibernatehibernate
I am going to assume hibertnatehibernate is not the correct value there. :)
Let me know if you want a bug filed.
Thanks,
Craig