Console Output

08:33:34 + docker build -t dockerbuildbot/docker-py:py2-5dea12f791bb8771553d21478015548bd7bb877f -f tests/Dockerfile --build-arg PYTHON_VERSION=2.7 .
08:33:34 Sending build context to Docker daemon  1.303MB

08:33:34 Step 1/19 : ARG PYTHON_VERSION=3.7
08:33:34 Step 2/19 : FROM python:${PYTHON_VERSION}
08:33:34  ---> 68e7be49c28c
08:33:34 Step 3/19 : ARG APT_MIRROR
08:33:34  ---> Using cache
08:33:34  ---> 733dc05c5fd9
08:33:34 Step 4/19 : RUN sed -ri "s/(httpredir|deb).debian.org/${APT_MIRROR:-deb.debian.org}/g" /etc/apt/sources.list  && sed -ri "s/(security).debian.org/${APT_MIRROR:-security.debian.org}/g" /etc/apt/sources.list
08:33:34  ---> Running in 558dff33739f
08:33:34 cgroups: cgroup mountpoint does not exist: unknown