As far as I can tell we're not gating on this right now. From
a quick glance, it looks like Debian stable has `libsodium-dev`
but only Ubuntu eoan does which we're not testing right now.
I think tests/ should be just that, ci/ is separate. Also rename
the files to include "travis" since that's what we use them
for right now.
Closes: #843
Approved by: jlebon