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

[Robert Ancell]

Ah, the USG button fix wasn't pushed to this branch - it was only in the PPA.
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https://code.launchpad.net/~robert-ancell/software-properties/+git/software-properties/+merge/430260
Your team Ubuntu Core Development Team is requested to review the proposed merge of ~robert-ancell/software-properties:ubuntu-pro-merge into software-properties:ubuntu/master.