`scripts/before_test.sh` has functionality that is required beyond this package

This script is responsible for 2 actions:

• pulling images for running tests
• compiling c++-backend algorithms for testing

An equivalent script exists in beat.cmdline. This script is also called inside beat.web.

To align with a better DRY policy, the functionality of this script should be python-ified and provided as a service to callers. This problem relates to having a saner implementation beat.web#510 (closed).

At this point, it may be desirable to update docker-py and related dependencies on our CI.