Code review comment for lp:~alan-griffiths/mir/fix-1717910

FAILED: Autolanding.
More details in the following jenkins job:
https://mir-jenkins.ubuntu.com/job/mir-autolanding/1427/
Executed test runs:
    FAILURE: https://mir-jenkins.ubuntu.com/job/build-mir/5027/console
    None: https://mir-jenkins.ubuntu.com/job/generic-land-mp/1559/console
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-0-fetch/5261
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-1-sourcepkg/release=artful/5249
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-1-sourcepkg/release=xenial/5249
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-1-sourcepkg/release=zesty/5249
    FAILURE: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=clang,platform=mesa,release=artful/5070/console
    ABORTED: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=clang,platform=mesa,release=zesty/5070/console
    ABORTED: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=gcc,platform=mesa,release=xenial/5070/console
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=cross-armhf,compiler=gcc,platform=mesa,release=artful/5070
        deb: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=cross-armhf,compiler=gcc,platform=mesa,release=artful/5070/artifact/output/*zip*/output.zip
    ABORTED: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=i386,compiler=gcc,platform=mesa,release=xenial/5070/console