When updating BYCEPS to a newer version, the set of required Python packages may change (additions, version upgrades/downgrades, removals).
Before continuing, make sure that the virtual environment is set up and activated.
(venv)$ pip install --upgrade pip
Then instruct pip to install the required Python depdendencies (again, the same way as during the installation):
(venv)$ pip install -r requirements.txt
This will install new but yet missing packages and upgrade/downgrade existing packages. It will not remove no longer used packages, though, but that should not be an issue.
If you want to run the test suite and/or use development tools, update their requirements as well:
(venv)$ pip install -r requirements-dev.txt