Please consider merging branch sbuild-fixes of repo https://git.spwhitton.name/propellor.
User-visible changes, excerpted from changelog:
* Using ccache with Sbuild.built & Sbuild.builtFor is now toggleable: these
properties now take a parameter of type Sbuild.UseCcache. (API Change)
* Sbuild.piupartsConf: no longer takes an Apt.Url. (API Change)
* Sbuild.piupartsConf & Sbuild.piupartsConfFor: does nothing if corresponding
schroot not built.
Previously, these properties built the schroot if it was missing.
* Sbuild.built & Sbuild.piupartsConf: add an additional alias to sid chroots.
This is for compatibility with `dgit sbuild`.
* Further improvements to Sbuild.hs haddock.