[Bug 2087935] Re: DeprecationWarning for multi-threaded fork() under Python 3.12

[Marcel Gast]

This bug also affects us on Ubuntu 24.04.1 LTS.

When I run unattended-upgrade in debug mode, this error message appears
after the packages have been downloaded, after the message “dpkg is
configured not to cause conffile prompts” before the program starts
installing the updates.

Debian seems to be discussing the bug at this address: 
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1076097

** Bug watch added: Debian Bug tracker #1076097
   https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1076097

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https://bugs.launchpad.net/bugs/2087935

Title:
  DeprecationWarning for multi-threaded fork() under Python 3.12

Status in unattended-upgrades package in Ubuntu:
  Confirmed

Bug description:
  We run unattended-upgrades on a lot of servers, but on Ubuntu noble (Ubuntu 24.04.1 LTS) we're getting a lot of cron spam that doesn't appear elsewhere:
  > /usr/bin/unattended-upgrade:567: DeprecationWarning: This process (pid=475626) is multi-threaded, use of fork() may lead to deadlocks in the child.
  > pid = os.fork()

  The above message appears several times during an upgrade; the count
  is different each week, presumably relating to what operations are
  needed.

  lsb_release -rd:
  No LSB modules are available.
  Description:	Ubuntu 24.04.1 LTS
  Release:	24.04

  Relevant packages:
  unattended-upgrades  2.9.1+nmu4ubuntu1
  python3.12           3.12.3-1ubuntu0.2

  The warning appears to be introduced in Python 3.12 - https://docs.python.org/3/whatsnew/3.12.html
  > On POSIX platforms, os.fork() can now raise a DeprecationWarning when it can detect being called from a multithreaded process

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