ci: Set image to debian:trixie

Signed-off-by: Wiktoria Kuna <[email protected]>

.ci.yml

@@ -1,16 +1,17 @@
-image: $DOCKER_IMAGE
+image: debian:trixie
 
 .build_setup: &setup_env
   before_script:
     - export DEBIAN_FRONTEND=noninteractive
-    - apt --allow-releaseinfo-change update && apt install -y --no-install-recommends git build-essential make python3 python3-pip
+    - apt --allow-releaseinfo-change update && apt install -y --no-install-recommends git build-essential make python3 python3-pip python3.11-venv
     - apt install -y --no-install-recommends apt-transport-https curl gnupg graphicsmagick-imagemagick-compat default-jdk default-jre
     - echo "deb https://repo.scala-sbt.org/scalasbt/debian all main" | tee /etc/apt/sources.list.d/sbt.list
     - echo "deb https://repo.scala-sbt.org/scalasbt/debian /" | tee /etc/apt/sources.list.d/sbt_old.list
     - curl -sL "https://keyserver.ubuntu.com/pks/lookup?op=get&search=0x2EE0EA64E40A89B84B2DF73499E82A75642AC823" | apt-key add
     - apt update && apt install -y sbt
     - git submodule update --init --recursive
-    - pip3 install -r docs/requirements.txt
+    - python3 -m venv .venv
+    - .venv/bin/python3 -m pip install -r docs/requirements.txt
 
 build-and-test:
   <<: *setup_env
@@ -27,6 +28,7 @@ build-docs:
   <<: *setup_env
   stage: build
   script:
+    - source .venv/bin/activate
     - SPHINXOPTS="-A conf_py_path=$DOCS_DIR/$SOURCEDIR/ -A commit=$CI_BUILD_REF -A branch=$CI_BUILD_REF_NAME" make html
     - make linkcheck
     - cp docs/*.png build/html