Cannot run log analytics in Matomo docker container due to lack of python3

Question

I have the following docker-compose file to run Matomo:

version: "2"

services:
  matomo:
    image: matomo
    environment:
      - MATOMO_DATABASE_HOST=matomo_db
      - VIRTUAL_HOST=webmon.extinctionrebellion.uk
    env_file:
      - ./db.env
    ports:
      - 8088:80
    volumes:
      - ./config:/var/www/html/config:rw
      - ./logs:/var/www/html/logs
      - ./matomo:/var/www/html
    depends_on:
      - matomo_db
    restart: unless-stopped

  matomo_db:
    container_name: matomo_db
    image: mariadb
    command: --max-allowed-packet=64MB
    environment:
      - MYSQL_ROOT_PASSWORD=passwordredacted
    env_file:
      - ./db.env
    volumes:
      - ./mysql/:/var/lib/mysql
    restart: unless-stopped

I mostly use Matomo for analysing log files, so I have a shell script that imports them, using the command:

cat /var/log/nginx/myserver.access.log.1 /var/log/nginx/myserver.access.log | docker-compose exec -T matomo python3  misc/log-analytics/import_logs.py --url='http://localhost' --idsite=mysiteid -

I have recently updated Matomo, and nothing works now, because python3 is not installed in my matomo image. I tried to install it by entering the container and running apt-get, but the command was not found. I tried building an alternative image based on matomo, but with additional commands to install python3, but apt-get update wouldn't work because4 of missing pubkeys. I tried adding the pubkeys but it complains about missing gpg packages.

Help - I'm stuck!

[Later] I saw the instructions at https://github.com/matomo-org/docker#docker-compose-examples-and-log-import-instructions which implied you had to run python in a different container. I tried starting up a python container and running the import, but I got these errors:

Traceback (most recent call last):
  File "/var/www/html/misc/log-analytics/import_logs.py", line 2690, in <module>
    main()
  File "/var/www/html/misc/log-analytics/import_logs.py", line 2652, in main
    recorders = Recorder.launch(config.options.recorders)
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/var/www/html/misc/log-analytics/import_logs.py", line 1828, in launch
    t.start()
  File "/usr/local/lib/python3.11/threading.py", line 957, in start
    _start_new_thread(self._bootstrap, ())
RuntimeError: can't start new thread
read unix @->/var/run/docker.sock: read: connection reset by peer