piuparts fail on: /usr/bin/bash: line 211: docker: command not found

I noticed today that two of my projects are both failing on:

Executing "step_script" stage of the job script
Using docker image sha256:7ff5b656d6aff11a05eca232e608eee64f19f67fd4472973d1be61a434711931 for registry.salsa.debian.org/salsa-ci-team/pipeline/piuparts:latest with digest registry.salsa.debian.org/salsa-ci-team/pipeline/piuparts@sha256:34e5f443f8d9b353eea0fe52d7d1fb735465a3cac37f0925e96f42ea0c1bfac7 ...
$ CHROOT_PATH="/tmp/debian-chroot"
$ CONTAINER_ID=$(docker run --rm -d "${SALSA_CI_IMAGES_BASE}" sleep infinity)
/usr/bin/bash: line 211: docker: command not found
Cleaning up project directory and file based variables
ERROR: Job failed: exit code 1

Examples:

• https://salsa.debian.org/otto/galera/-/jobs/6030424
• https://salsa.debian.org/debian/debcraft/-/jobs/6030541
• https://salsa.debian.org/salsa-ci-team/pipeline/-/jobs/6030472

I suspect this is a recent regression, but I am unable to pointpoint what.