With the sources.list below this works:

```
"apt-get" "-o" "Debug::pkgDepCache::AutoInstall=false" "-o" "APT::Get::Show-Versions=false" "-u" "dist-upgrade" "--print-uris" "--yes" "-t"  bookworm-security
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
Calculating upgrade... Done
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
```

while this gives an error:

```
# "apt-get" "-o" "Debug::pkgDepCache::AutoInstall=false" "-o" "APT::Get::Show-Versions=false" "-u" "dist-upgrade" "--print-uris" "--yes" "-t"  bookworm-updates
Reading package lists... Done
E: The value 'bookworm-updates' is invalid for APT::Default-Release as such a release is not available in the sources
```

I assume that's because there's not yet a point release for bookworm and
hence the Packages file is empty. This currently trips up the munin
apt_all plugin on bookworm. I'm aware there's better ways to figure out missing
upgrades but wanted to report it nevertheless.

Cheers,
 -- Guido

This now also occurs for hosts with trixie sources configured. Adding
sources that are valid but empty is intentional, as otherwise often months
would elapse between sources becoming non-empty and me noticing (which is a
problem for *-security!).  ���

At the moment, munin-node's `apt_all update` cron job results in complaints
about these sources:

  E: The value 'buster-proposed-updates-debug' is invalid for APT::Default-Release as such a release is not available in the sources
  E: The value 'trixie-backports' is invalid for APT::Default-Release as such a release is not available in the sources
  E: The value 'trixie-security' is invalid for APT::Default-Release as such a release is not available in the sources
  E: The value 'trixie-updates' is invalid for APT::Default-Release as such a release is not available in the sources

My kitchen-sink apt config follows. This machine (actually an LXD container)
is nominally bookworm but has trixie and unstable sources available but
pinned appropriately.