Comment 1 for bug 1843355

https://launchpad.net/bugs/1842969
<cjwatson> note that if you're doing this then you need to do an Ubuntu-local reintroduction of python-tblib (the py2 binary package) as a build-dependency
<cjwatson> possibly some other stuff on https://people.canonical.com/~ubuntu-archive/nbs.html