[Merge] ~nteodosio/software-properties:attach-url into software-properties:ubuntu/master

[Nathan Teodosio]

For visual reference for Oliver: I posted an image of that in https://chat.canonical.com/canonical/pl/g5iwf5muqbg3z87hq8hmay56yc
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https://code.launchpad.net/~nteodosio/software-properties/+git/software-properties/+merge/454886
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