fail2ban fails to start on 22.04 (cannot import name 'MutableMapping' from 'collections' py3.10)

hotfix: `cd /usr/bin;ln -sf python3.9 /usr/bin/python3`

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

Simple fix here, which will need to be applied until a new version of Fail2ban with the fix included is released.
https://github.com/fail2ban/fail2ban/commit/294ec73f629d0e29cece3a1eb5dd60b6fccea41f

Applying the fix in github resulted in a different error:

ail2ban.service - Fail2Ban Service
     Loaded: loaded (/lib/systemd/system/fail2ban.service; enabled; vendor preset: enabled)
     Active: failed (Result: exit-code) since Thu 2022-03-10 14:51:00 PST; 5s ago
       Docs: man:fail2ban(1)
    Process: 22282 ExecStartPre=/bin/mkdir -p /run/fail2ban (code=exited, status=0/SUCCESS)
    Process: 22283 ExecStart=/usr/bin/fail2ban-server -xf start (code=exited, status=255/EXCEPTION)
   Main PID: 22283 (code=exited, status=255/EXCEPTION)
        CPU: 33ms

Mar 10 14:51:00 nanook systemd[1]: Starting Fail2Ban Service...
Mar 10 14:51:00 nanook systemd[1]: Started Fail2Ban Service.
Mar 10 14:51:00 nanook fail2ban-server[22283]: ERROR: No module named 'ConfigParser'
Mar 10 14:51:00 nanook systemd[1]: fail2ban.service: Main process exited, code=exited, status=255/EXCEPTION
Mar 10 14:51:00 nanook systemd[1]: fail2ban.service: Failed with result 'exit-code'.

That did make it work but linking to a previous version of python rather than fixing the application so that it does not use a deprecated function does not seem like a good long term solution.

@robert i wasnt claiming long term fix, just a hot fix for people that want fail2ban to just freaking work while having public ip and sshd running 24/7. thank you for telling me what i already knew perfectly well, waiting for the final fix for what the vendor is shipping

Ok, hopefully a real fix by the time 22.04 becomes official. I upgraded workstation early just to find these kind of problems ahead of upgrading servers. Thank you.

This bug was fixed in the package fail2ban - 0.11.2-6

---------------
fail2ban (0.11.2-6) unstable; urgency=medium

  * Cherry-pick upstream fix to fix a startup issue with Python 3.10
    (LP: #1958505)
  * Cherry-pick upstream fix for courier-auth (Closes: #1004466)
  * ignore false positive
    fail2ban: read-in-maintainer-script [postinst:41

 -- Sylvestre Ledru <email address hidden> Thu, 10 Mar 2022 22:52:59 +0100

I can confirm that fail2ban now works as expected.

service fail2ban status
● fail2ban.service - Fail2Ban Service
     Loaded: loaded (/lib/systemd/system/fail2ban.service; enabled; vendor preset: enabled)
     Active: active (running) since Tue 2022-03-22 16:07:45 GMT; 6s ago
       Docs: man:fail2ban(1)
   Main PID: 64422 (fail2ban-server)
      Tasks: 27 (limit: 38025)
     Memory: 16.4M
        CPU: 3.890s
     CGroup: /system.slice/fail2ban.service
             └─64422 /usr/bin/python3 /usr/bin/fail2ban-server -xf start

Mar 22 16:07:45 nova systemd[1]: Started Fail2Ban Service.
Mar 22 16:07:46 nova fail2ban-server[64422]: Server ready
root@nova:/usr/bin# ll python3
lrwxrwxrwx 1 root root 10 Mar 22 16:07 python3 -> python3.10*

Confirmed, it works for me with python3.10 now as well. Thank you!