babune is now able to run -proposed for SRUs

[Martin Pool]

I hope we'll soon extend this to also test the beta and daily ppas,
which will have a higher rate of change and so probably find more
exciting results.  Using a schroot snapshot to install into a minimal
clean environment should be useful.  I'd also like to use this to test
whether bzr and its plugins are all simultaneously mutually
installable and whether they pass their test suites.

Martin