run-tests: include non-activated venv packages in `PYTHONPATH`...
run-tests: include non-activated venv packages in `PYTHONPATH`
If a venv is activated since afa9d73780e1, `hghave` would see the packages
installed in it, and enable related tests. If the python interpreter was
launched directly however, none of them were seen.
In addition to getting consistent behavior, it's also easier to manage in CI if
the venv doesn't need activation.