ERROR: Could not create cache adapter

Summary

When running the job, this error come up. Nevertheless, the job finishes with success. Version 11.5 -> ERROR: Could not create cache adapter
error=cache factory not found: factory for cache adapter "" was not registered

Steps to reproduce

1. It happens with any job in the gitlab-ci.yml, for example:

.cache_assets: &cache_assets
  stage: cache
  script:
    - cd client
    - yarn install
    - yarn run dist
  artifacts:
    paths:
      - client/dist
    when: on_success
    expire_in: 1 days

2. In the runner console, I will get: error=cache factory not found: factory for cache adapter "" was not registered

3. The job finishes as expected and cache folder is created.

Expected behavior

This error should not appear.

Environment description

This is the toml description:

[[runners]]
  name = "name-of-the-runner"
  url = "https://gitlab.com/"
  token = "XXXXXX"
  executor = "docker"
  shell = "bash"
  cache_dir = "/home/cache"
  [runners.docker]
    tls_verify = false
    image = "image/image.1.0"
    privileged = false
    disable_cache = false
    volumes = ["/home/aks:/root/.kube/", "/home/cache:/cache:rw", "/var/run/docker.sock:/var/run/docker.sock"]
    shm_size = 268435456
  [runners.cache]
    [runners.cache.s3]
    [runners.cache.gcs]

Used GitLab Runner version

Version: 11.5.0 Git revision: 3afdaba6 Git branch: 11-5-stable GO version: go1.8.7 Built: 2018-11-22T09:20:06+0000 OS/Arch: linux/amd64

Bug Investigation and analysis tasks: workflowrefinement

• Setup test environment.
• Attempt to reproduce the bug.
• If bug can be reproduced, analyze logs and determine the possible root cause.
• Update the proposal section in the desription with the proposed fix, including a note on level of effort.

Proposed fix

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