Comment 8 for bug 1906245

Test:
# install current version - will be >=1:5.1+dfsg-4ubuntu2
$ apt install qemu-system-gui
# get old broken version and install it
$ wget https://launchpad.net/ubuntu/+source/qemu/1:5.1+dfsg-4ubuntu1/+build/20311790/+files/qemu-system-gui_5.1+dfsg-4ubuntu1_amd64.deb
$ dpkg --force-all -i qemu-system-gui_5.1+dfsg-4ubuntu1_amd64.deb
# trigger the bug
$ apt install qemu-system-gui
...
Preparing to unpack .../qemu-system-gui_1%3a5.1+dfsg-4ubuntu2_amd64.deb ...
cp: -r not specified; omitting directory '/var/run/qemu/Debian'
dpkg: warning: old qemu-system-gui:amd64 package pre-removal script subprocess returned error exit status 1
dpkg: trying script from the new package instead ...
dpkg: error processing archive /var/cache/apt/archives/qemu-system-gui_1%3a5.1+dfsg-4ubuntu2_amd64.deb (--unpack):
 there is no script in the new version of the package - giving up
Errors were encountered while processing:
 /var/cache/apt/archives/qemu-system-gui_1%3a5.1+dfsg-4ubuntu2_amd64.deb
E: Sub-process /usr/bin/dpkg returned an error code (1)

A fixed version builds in [1] and will be tested before uploading the fix (no other changes than for this bug in this)

[1]: https://launchpad.net/~ci-train-ppa-service/+archive/ubuntu/4356