trees extension doesn't work with hg 3.8.3

[Doug Simon]

server3:~ graal$ hg version
Mercurial Distributed SCM (version 3.8.3)
(see https://mercurial-scm.org for more information)

Copyright (C) 2005-2016 Matt Mackall and others
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
server3:~ graal$ hg --config extensions.trees=trees/trees.py tclone --noupdate http://hg.openjdk.java.net/jdk9/hs-comp
*** failed to import extension trees from trees/trees.py: 'module' object has no attribute 'norepo'
hg: unknown command 'tclone'
(did you mean clone?)

It works fine with Mercurial 3.5.2 so it seems like the commands.norepo and commands.optionalrepo attributes were removed in between.

-Doug