Fix some virtualenv errors

Firstly, using 'python -m venv' doesn't require a previous global install of virtualenv; so it can work on fresh containers (like
the CI runners). Secondly, the activation needs to be 'sourced' so it affects the current shell execution
2 jobs for summarize-in-pipeline in 7 seconds (queued for 1 second)
Status Name Job ID Coverage
passed generate-pipeline #74175


failed execute-tests