This should eliminate differences between setups on different machines.
This project doesn't need system packages, everything can be installed
from PyPI. That's also the same approach that is recommended in README.
The current state was probably just a copy-paste from a different
project.
Also remove --force-reinstall from pip command line, it has no
effect when --upgrade is not present.
If you approve this, I'll make the same change also to #resultsdb_api and #resultsdb_frontend.