gitlab ci cache and python virtualenv issues warnings for symlinked files on re-use "WARNING: ...: chmod ...: no such file or directory"

when caching a python virtualenv you're greeted with a disturbing warning block like this https://gitlab.com/joernhees/test_ci_symlinks/builds/2320720

I think that in its current form these are issued for symlinked files ln -s ... ... in the cached folder.

I made a public test repo https://gitlab.com/joernhees/test_ci_symlinks , which just contains this .gitlab-ci.yml:

test:
  stage: test
  image: python:2
  tags:
    - docker
  cache:
    paths:
      - venv/
  script:
    - virtualenv -q venv
    - source venv/bin/activate
    - pip install -Uq flask
    - ls -FlahR

I then ran the tests here: https://gitlab.com/joernhees/test_ci_symlinks/pipelines/3688415 . You can see that the first run is quite ok and fills the cache. I then re-ran the build to make use of the cache, causing the said warnings in the second run.

As you can see from the output of the ls -FlahR the warnings seem to be generated from symlinked files.

Is the problem maybe related to zipping the cache folder? Is there a way to use tar.gz instead?

~CI