Comment 1 for bug 1657440

The proxy shows no attempts to download Release.gpg, just InRelease:

18/Jan/2017:12:29:02 +0000 69 y.y.y.y TCP_MISS/404 631 GET http://ubuntu-cloud.archive.canonical.com/ubuntu/dists/xenial-updates/newton/InRelease - FIRSTUP_PARENT/x.x.x.x text/html
18/Jan/2017:12:29:02 +0000 67 y.y.y.y TCP_REFRESH_UNMODIFIED/304 335 GET http://ubuntu-cloud.archive.canonical.com/ubuntu/dists/xenial-updates/newton/Release - FIRSTUP_PARENT/x.x.x.x -
18/Jan/2017:12:29:02 +0000 133 y.y.y.y TCP_REFRESH_UNMODIFIED/304 420 GET http://archive.ubuntu.com/ubuntu/dists/xenial/InRelease - FIRSTUP_PARENT/x.x.x.x -
18/Jan/2017:12:29:02 +0000 134 y.y.y.y TCP_REFRESH_UNMODIFIED/304 438 GET http://security.ubuntu.com/ubuntu/dists/xenial-security/InRelease - FIRSTUP_PARENT/x.x.x.x -
18/Jan/2017:12:29:02 +0000 67 y.y.y.y TCP_REFRESH_UNMODIFIED/304 423 GET http://archive.ubuntu.com/ubuntu/dists/xenial-updates/InRelease - FIRSTUP_PARENT/x.x.x.x -
18/Jan/2017:12:29:02 +0000 66 y.y.y.y TCP_REFRESH_UNMODIFIED/304 420 GET http://archive.ubuntu.com/ubuntu/dists/xenial-backports/InRelease - FIRSTUP_PARENT/x.x.x.x -