[Merge] ~nteodosio/software-properties:xenial-ua into software-properties:ubuntu/xenial

[Nathan Teodosio]

I was able to reproduce the error in a new Xenial virtual machine, though my old one was still fine with it... ¯\_(ツ)_/¯

Thanks for the review, I addressed your comments.
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https://code.launchpad.net/~nteodosio/software-properties/+git/software-properties/+merge/448388
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