Missing files

I have a legacy python app which uses celery==3.1.26.post2 and the official image python:2.7.18-slim-buster.

When I run docker-slim --http-probe=false my/image it goes from ~180MB to ~49MB, that's cool. But there are some celery files missing, in my case /usr/local/lib/python2.7/site-packages/celery/worker/strategy.py. The app code is copied to /app/tasks.

Then I tried building an image using python:3.8.5-slim-buster. This time the code at /app/tasks is missing and /usr/local/lib/python3.8/site-packages/celery/worker (the whole directory) too. I guess this scenario fails because the app doesn't work on Python 3 due to import failures in the dependencies, but the missing app code really caught my eye, or maybe I missed something?

The Dockerfile goes like this:

ARG PYTHON_VERSION=2.7.18

FROM python:${PYTHON_VERSION}-slim-buster AS base
WORKDIR /app
COPY requirements.txt .
RUN pip install --no-cache-dir -r requirements.txt

FROM base AS release
COPY tasks tasks
USER nobody
ENV PYTHONWARNINGS=ignore
ENV PYTHONUNBUFFERED=1
ENTRYPOINT ["celery", "worker", "--app=tasks", "--pool=eventlet"]
CMD ["--loglevel=INFO", "--concurrency=100"]

requirements.txt:

requests[security]==2.19.1
soundcloud==0.5.0
celery==3.1.26.post2
kombu==3.0.37
eventlet==0.24.1
python-json-logger==0.1.11
sentry-sdk==0.16.3
six==1.15.0

Version:

$ ./docker-slim --version
docker-slim version linux|Transformer|1.32.0|10b628fc3cd9f903237b9c31a6aba5ac4e6bc9c8|2020-08-24_06:14:32AM

Start with the reported docker-slim 1.32.0 command and the supplied Dockerfile and requirements.txt. Reproduce the image-minification run for the Python 2.7 and 3.8 variants, then inspect whether /app/tasks and the reported celery paths are retained. Done means the cause of the missing files is identified and the affected paths are handled consistently or the behavior is documented.