relnotes: enable extension when running releasenotes command
Last night, when I was working on different machine, the test worked, now on a
different machine it does not. Looks like we should make sure releasenotes
extension is loaded.
Differential Revision: https://phab.mercurial-scm.org/D4425
\{
"node": {node|json},
"changeset_count": {changesets|json},
"changesets": [{join(nodes%graphentry, ", ")}]
}