100% coverage for Xenial

There's a related issue which should be fixed for Xenial as well. When running the test suite locally in a xenial chroot, `sudo` will fail with the following error:

sudo: no tty present and no askpass program specified

So I need to find a way to run sudo w/o asking for the password in the autopkgtests w/o changing that behavior in production.

Possible approaches:

* Add $AUTOPKGTEST_NORMAL_USER to sudoers in the test script and add a breaks-testbed Restriction
* Mock the sudo to add -A or -n
* Set $SUDO_ASKPASS to something in the autopkgtests

On Thu, Oct 27, 2016 at 02:25:29PM -0000, Barry Warsaw wrote:
> Possible approaches:

> * Add $AUTOPKGTEST_NORMAL_USER to sudoers in the test script and add a breaks-testbed Restriction
> * Mock the sudo to add -A or -n
> * Set $SUDO_ASKPASS to something in the autopkgtests

 * skip wrapping the mkfs.ext4 invocation in 'sudo' when uid == 0

Oh, I like that, great idea.

Of course, it still means we'd need `Restriction: needs-root` so I'm not sure how much of an advantage that is. I.e. I don't think it really buys you much.

OTOH, since we're releasing each distroseries from a different branch, maybe we just enable `Restriction: needs-root` for the py35 and coverage autopkgtests on the xenial branch and be done with it.