It broke too: https://jenkins.tails.boum.org/job/test_Tails_ISO_stable/78/

refs: #10774

* Ruby doesn't support keyword arguments when calling; for a method
  defined as f(x = y), calling it with f(x = z) will actually create a
  local variable x in the scope f was called from.

* Since we only care whether withgpgapplet is nil or not, we don't
  have to reintroduce @withgpgapplet with the same property.

It's currently a problem on Debian Sid with libvirt 1.2.21-2 and
libguestfs <= 1:1.28.12-1+b3.

In Jessie's GNOME we don't have arrows on the scrollbars, so it's hard
to find a good image identifying the right part to click to scroll
up. Luckily Page Up/Down are mapped to scrolling the chat log, so we
can use that instead.

Have the security advisory against 1.7 point to 1.8.1, since 1.8 doesn't fix all issues fixed in here.