[Merge] ~robert-ancell/software-properties:esm into software-properties:ubuntu/master

[Robert Ancell]

See https://code.launchpad.net/~robert-ancell/software-properties/+git/software-properties/+merge/400302 for the backported change in xenial.
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https://code.launchpad.net/~robert-ancell/software-properties/+git/software-properties/+merge/400153
Your team Ubuntu Core Development Team is requested to review the proposed merge of ~robert-ancell/software-properties:esm into software-properties:ubuntu/master.