Final Focal on Kubuntu 20.04

[NoWorries]

Another small problem that arose this morning is that Muon is no longer working. I found that it was no longer installed on my system and when I tried to install it, I got the error message

sudo apt install muon
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies.
muon : Depends: apt-xapian-index but it is not going to be installed
E: Unable to correct problems, you have held broken packages.

This problem impacts all systems, so will have to wait for a fix.

[Snowhog]

Performing an update and full-upgrade on my 20.04 system 'as I type'. I noticed that:

Removing muon (4:5.8.0-1ubuntu5) ...
Removing apt-xapian-index (0.49ubuntu3) ...
Removing index /var/lib/apt-xapian-index...

I'll verify or disprove that Muon Package Manager isn't available after the full-upgrade completes.

[Snowhog]

Nope. Muon was removed. Here is the 'trail':

The following packages have unmet dependencies:
muon : Depends: apt-xapian-index but it is not going to be installed
E: Unable to correct problems, you have held broken packages.

The following packages have unmet dependencies:
apt-xapian-index : Depends: python3-apt (>= 0.7.93.2) but it is not going to be installed
E: Unable to correct problems, you have held broken packages.

python3-apt is already the newest version (1.9.10).
python3-apt set to manually installed.

So, it looks (to me) that the issue is a problem with packaging version information with python3-apt.

[acheron]

There is no breakage in the release pocket.

Again, this is because of using -proposed. The package is question causing it is python-apt.

python-apt (1.9.10) unstable; urgency=medium

* Improve type annotations for apt_pkg.TagFile and apt_pkg.TagSection.
  Thanks to Stuart Prescott for the report that object was ... wrong
* [B]Break broken kthresher and apt-xapian-index versions[/B]

One of the reasons python-apt is STILL in proposed, is that it causes other things to be removed and/or be uninstallable. In this case apt-xapian-index, which muon depends on.

This can be seen in the output of the proposed migration run.

trying: python-apt
skipped: python-apt (38, 0, 58)
 got: 51+0: a-17:a-8:a-8:i-2:p-8:s-8
 * amd64: [B]apt-xapian-index, kde-full, kde-standard, kthresher, kubuntu-driver-manager, kubuntu-driver-manager-dbg, muon, packagesearch, ubuntu-kylin-software-center[/B]

i.e. if python-apt was to migrate to release, that list of packages would break as a result. So migration is skipped, and it stays in proposed.

DON'T USE THE PROPOSED POCKET. It exists as a QA barrier to protect the release pocket from such breakage, NOT as a way to get cool new things sooner!

[Snowhog]

Okay, I did have the proposed repository active. I just commented it out, updated the database (sudo updatedb) and simulated an install of muon:

The following packages have unmet dependencies:
muon : Depends: apt-xapian-index but it is not going to be installed
E: Unable to correct problems, you have held broken packages.

The following packages have unmet dependencies:
apt-xapian-index : Depends: python3-apt (>= 0.7.93.2) but it is not going to be installed
E: Unable to correct problems, you have held broken packages.

python3-apt is already the newest version (1.9.10).
python3-apt set to manually installed.

So, here at least, I still can't install Muon after disabling the proposed repository.

Is the problem with python3-apt? There is a package called python-apt, and both packages have identical version information.

[acheron]

Is the problem with python3-apt? There is a package called python-apt, and both packages have identical version information.

Yes, the python-apt I was referring to earlier is the python-apt source package from which python3-apt and python-apt debs are built. The actual deb with the breaks on apt-xapian-index is the python3 one.

[Snowhog]

So, if I purge python3-apt and install python-apt, I should then be able to install muon?

Added:

I just simulated the installation of python-apt:

The following additional packages will be installed:
libpython2-stdlib libpython2.7-minimal libpython2.7-stdlib python2 python2-minimal python2.7 python2.7-minimal
Suggested packages:
python-apt-dbg python-apt-doc python2-doc python-tk python2.7-doc binfmt-support
The following NEW packages will be installed:
libpython2-stdlib libpython2.7-minimal libpython2.7-stdlib python-apt python2 python2-minimal python2.7 python2.7-minimal
0 upgraded, 8 newly installed, 0 to remove and 0 not upgraded.

Is this the preferred way?

[acheron]

No, you need to downgrade it to the version in the release pocket

[Snowhog]

Hmm. Well, I went ahead and installed python-apt, which removed python3-apt. Still can't install Muon. So, should I/we 'downgrade to the version in the release pocket' or wait? And if the former, how does one do that?

[acheron]

sudo apt-get install muon apt-xapian-index python3-apt=1.9.8

[GreyGeek]

Running muon 4:5.8.0-1ubuntu5 here and even after around 500 updates, additions & removals muon and apt-xapian-index are still on my system.

[Snowhog]

sudo apt-get install muon apt-xapian-index python3-apt=1.9.8

Thank you. That works.

So, python3-apt is the 'necessary' package at version 1.9.8. What then is python-apt for, which is also at the same version?

[acheron]

What then is python-apt for, which is also at the same version?

That is the python 2 version. Not much needs it any more, but there are a few things.

$ reverse-depends python-apt
Reverse-Recommends
==================
* python-debian

Reverse-Depends
===============
* python-apt-dbg
* python-apt-dev
* xdeb

[NoWorries]

sudo apt-get install muon apt-xapian-index python3-apt=1.9.8

Many thanks for that. It worked for me as well and after doing that, I got the message:

The following package was automatically installed and is no longer required:
python3-xapian
Use 'sudo apt autoremove' to remove it.
The following packages will be REMOVED
apt-xapian-index muon
The following packages will be upgraded:
python3-apt
1 to upgrade, 0 to newly install, 2 to remove and 0 not to upgrade.
Need to get 154 kB of archives.
After this operation, 2,427 kB disk space will be freed.
Do you want to continue? [Y/n]

This message was no longer present after using Muon to disable proposed.

I will now have to remove synaptic which was my standby when Muon failed to install. Looks like I will have to stick with no proposed option until this problem is resolved in python3.

[kubicle]

DON'T USE THE PROPOSED POCKET. It exists as a QA barrier to protect the release pocket from such breakage, NOT as a way to get cool new things sooner!

This can't be stressed enough, by using proposed repos you are testing things that don't need to be tested and reporting breakages that don't need to be reported. What you do with your machine is your business but reporting the issues you face and asking for help eats up other people's time as well, time that could be productively spent elsewhere.