The calc_release_version.py script uses the --merged option to the git command. Several older platforms (e.g., RHEL7, Debian 8, Ubuntu 14.04) have older versions of Git which do not support that option. As a result, many tasks on the waterfall are failing. This is the case on both the master branch and the r1.19 branch.

One option is to drop the --merged option, as was done in the C++ driver. Another option is to have a single task that executes version calculation step on a newer platform and then all other tasks can use that artifact with the pre-calculated as was done in the libmongocrypt project.