automated signoff fails on zesty, missing build on powerpc

[Olivier Tilloy]

Automated signoff failed on silo 2615 for zesty.
Copying output at https://bileto.ubuntu.com/excuses/2615/zesty.html:

  webbrowser-app (0.23+17.04.20170310-0ubuntu1 to 0.23+17.04.20170320.1-0ubuntu1)
    Maintainer: Ubuntu Developers
    0 days old
    missing build on powerpc: qml-module-ubuntu-web-doc, qtdeclarative5-ubuntu-web-plugin-doc, webapp-container-autopilot, webbrowser-app-autopilot (from 0.23+17.04.20170310-0ubuntu1)
    Not considered

According to https://lists.ubuntu.com/archives/ubuntu-devel-announce/2017-March/001206.html, « powerpc packages are no longer considered for proposed-migration, and we have discontinued all CD
image builds for powerpc in zesty ».

In the PPA associated to the silo, powerpc packages were not built at all for zesty, which seems intended, given the above. So it looks like there is an incorrect expectation in bileto/britney.