Vielleicht so?

.gitlab-ci.yml

@@ -2,8 +2,8 @@ image: python:latest
 
 before_script:
   - curl -sSL https://install.python-poetry.org | python3 -
-  - export PATH="$PATH:$HOME/.poetry/bin/" 
-  - source $HOME/.poetry/env 
+  - export PATH="/root/.local/bin:$PATH"
+  - poetry --version
 
 stages:
   - build_package