Comment 0 for bug 1959485

When updating from focal to jammy I found the following reproducible way to crash aptitude.

$ apt policy python3-chardet
python3-chardet:
  Installed: 3.0.4-4build1
  Candidate: 4.0.0-1
  Version table:
     4.0.0-1 500
        500 http://de.archive.ubuntu.com/ubuntu jammy/main amd64 Packages
        500 http://de.archive.ubuntu.com/ubuntu jammy/main i386 Packages
 *** 3.0.4-4build1 500
        500 http://de.archive.ubuntu.com/ubuntu focal/main amd64 Packages
        500 http://de.archive.ubuntu.com/ubuntu focal/main i386 Packages
        100 /var/lib/dpkg/status
$ apt policy python3-yaml
python3-yaml:
  Installed: 5.4.1-1ubuntu1
  Candidate: 5.4.1-1ubuntu1
  Version table:
 *** 5.4.1-1ubuntu1 100
        100 /var/lib/dpkg/status
     5.4.1-1 500
        500 http://de.archive.ubuntu.com/ubuntu jammy/main amd64 Packages
     5.3.1-1ubuntu0.1 500
        500 http://de.archive.ubuntu.com/ubuntu focal-security/main amd64 Packages
        500 http://de.archive.ubuntu.com/ubuntu focal-updates/main amd64 Packages
     5.3.1-1 500
        500 http://de.archive.ubuntu.com/ubuntu focal/main amd64 Packages

python3-chardet and python3-six cannot currently upgrade on my machine due to bug 1958720. Updated packages come in all the time for jammy at the moment. When I hit + on the section of "Upgradable Packages" in aptitude I am thus currently always breaking packages. Aptitude calculates a way for me to resolve the problem, usually holding a couple of packages at their current version. I accept and then aptitude still shows 2 broken packages (this is a bug in itself, I guess). I can verify with b that the broken packages are python3-chardet and python3-six. I can hold both packages with : and move on and nothing bad happens. But if I don't do that and instead rely on aptitude resolving conflicts before installing by hitting g, then aptitude will reliably crash.

$ sudo aptitude
Uncaught exception: ../../src/ui.cc:1549: void auto_fix_broken(): Assertion "resman->resolver_exists()" failed.