A network automation team runs a GitLab CE pipeline whose 'lint' job intermittently fails with 'nornir: command not found', while the same command succeeds when run locally. The .gitlab-ci.yml declares a global 'before_script' that installs dependencies with 'pip install -r requirements.txt', and the job also defines its own job-level 'before_script' that only runs 'python --version'. What is the most likely cause of the failure?