Code review comment for lp://staging/~mvo/ubuntu-release-upgrader/use-str.format

It might be a lot of work to port, but I will suggest using my flufl.i18n package, which has a lot of nice convenience APIs and safeguards for doing i18n interpolation.

http://pythonhosted.org/flufl.i18n/docs/using.html

And of course, it's packaged up :).