<ocdtrekkie>
It's entirely possible this will work if I delete that chunk, it seems reasonable that Debian doesn't maintain a "testing" branch for Stretch anymore.
<TimMc>
It's not so much a branch as an alias.
<TimMc>
or rather, at that time, I bet testing == buster
<ocdtrekkie>
That's what the commit message seems to suggest, but the Vagrantfile still says Stretch, but he also has commits in here about using Docker.
<ocdtrekkie>
So I'm now not confident this was packaged with vagrant-spk for it's last release. :|
<TimMc>
(OK, I guess they actually are branches, but the labels get promoted on each release and oldstable gets a permanent name.)
<ocdtrekkie>
I wonder why there is no Buster files if he had updated the sources to use Buster before the release. Maybe it's a branch that was merged in after?