Workaround for broken qemu-system-gui upgrade in Hirsute until 5.1+dfsg-4ubuntu3 lands

[Christian Ehrhardt]

Hi,
if you are upgrading packages in hirsute as of today you might see a
fail for the package qemu-system-gui. If you are not, be happy and
feel free to close this mail :-)

But if you are affected I first need to say sorry. Furthermore I
wanted to let you know that it is some unfortunate fallout of the
merge of qemu 5.1 which first triggered [2] for qemu-block-extra
(already fixed) and now [3] qemu-system-gui (similar but different).

Of course you can just wait for [1] to land in hirsute and upgrades
will work again without you having to do any else. But if you just
want to unblock your upgrades asap you should know that this issue is
only on the upgrade path when running the .prerm of the currently
installed version.
Therefore here a few manual workarounds that you could consider:

Workaround #1 - uninstall and install
$ apt remove qemu-system-gui
# the remove will complain the same way as the upgrade, but an install
# of the new version over this state "rH" works.
# You most likely had this installed through qemu-system-x86
# so remember to re-install dependency removed packages as well:
$ apt install qemu-system-x86 qemu-system-gui

Workaround #2 - use repackaged 5.1+dfsg-4ubuntu1 (If you can't remove
qemu* packages for some reason)
# replace original 5.1+dfsg-4ubuntu1 with one that does not have the prerm issue
$ wget https://bugs.launchpad.net/ubuntu/+source/qemu/+bug/1906245/+attachment/5439620/+files/qemu-system-gui_5.1+dfsg-4ubuntu1_amd64.repackaged.lp1906245.deb
$ dpkg -i qemu-system-gui_5.1+dfsg-4ubuntu1_amd64.repackaged.lp1906245.deb
# upgrade to 5.1+dfsg-4ubuntu2 (now working)
$ apt install qemu-system-gui

Workaround #3 - use the PPA version
$ sudo add-apt-repository ppa:ci-train-ppa-service/4356
$ apt install qemu-system-gui
# or
$ apt install upgrade
# This will need libgdk-pixbuf-2.0-0 from proposed thou

[1]: https://launchpad.net/ubuntu/+source/qemu/1:5.1+dfsg-4ubuntu3
[2]: https://bugs.launchpad.net/ubuntu/+source/qemu/+bug/1905377
[3]: https://bugs.launchpad.net/ubuntu/+source/qemu/+bug/1906245

-- 
Christian Ehrhardt
Staff Engineer, Ubuntu Server
Canonical Ltd