package python3-apt 1.6.0~rc2ubuntu2 failed to install/upgrade: subprocess new pre-removal script returned error exit status 127

Status changed to 'Confirmed' because the bug affects multiple users.

From the log file:

Preparing to unpack .../python3-apt_1.6.0~rc2ubuntu2_amd64.deb ...
/var/lib/dpkg/info/python3-apt.prerm: 6: /var/lib/dpkg/info/python3-apt.prerm: py3clean: not found
dpkg: warning: subprocess old pre-removal script returned error exit status 127
dpkg: trying script from the new package instead ...
/var/lib/dpkg/tmp.ci/prerm: 6: /var/lib/dpkg/tmp.ci/prerm: py3clean: not found
dpkg: error processing archive /var/cache/apt/archives/python3-apt_1.6.0~rc2ubuntu2_amd64.deb (--unpack):
 subprocess new pre-removal script returned error exit status 127

Does the file /usr/bin/py3clean exist on your system?

It does in my system:
chris@ubuntu-quadcore:~$ ls -l /usr/bin/py3clean
-rwxr-xr-x 1 root root 7806 Apr 10 10:48 /usr/bin/py3clean

py3clean is only executed if which tells us it exists:

if which py3clean >/dev/null 2>&1; then
        py3clean -p python3-apt
else

hence it's quite strange.

It should be finding that it exists and should execute that version based on the following little script that I just executed:

chris@ubuntu-quadcore:~$ if which py3clean >/dev/null 2>&1; then
> echo "IT EXISTS: `which py3clean`";
> fi
IT EXISTS: /usr/bin/py3clean

I fixed the display problem by running the following command, which appeared to work OK:

sudo apt-get install --reinstall python-apt

After that I opened "Settings" and on the "Screen Display" tab I then had the choice of choosing the proper video card driver. I chose it, and restarted, and I now have a sensible display setting of 1680*1050.

As a point of interest, when the display was set to 640*480 it was extremely difficult to use things like "Settings" due to the inability to scroll down on the wizard or the screen. Perhaps some testing of such things against what I presume is the default screen setting of 640*480 would make trouble shooting easier.

Thanks,
Chris