Authentication to pull image private registry for xcom sidecar

[robkuehl]

In my project I use airflow deployed in an Openshift Cluster. Several KubernetesPodOperators write to xcom and therefore use the xcom sidecar container which is pulled from docker hub. Unfortunately, we reached the pull limit for unregistered docker users. Now I would like to pull the alpine image for the sidecar container from a private gitlab registry.
Therefore I added the following to the values.yaml:

localSettings:
    ## the full content of the airflow_local_settings.py file (as a string)
    ## - docs for airflow cluster policies:
    ##   https://airflow.apache.org/docs/apache-airflow/stable/concepts/cluster-policies.html
    ##
    stringOverride: |
      # use a custom xcom_sidecar image for KubernetesPodOperator()
      from airflow.providers.cncf.kubernetes.utils.xcom_sidecar import PodDefaults
      PodDefaults.SIDECAR_CONTAINER.image = "registry.gitlab.com/privatepath/alpine:latest"

Now when I start the pipeline, In receive the following error:

Failed to pull image "registry.gitlab.com/cidecisiondesigngmbh/immotep/immotep-airflow-pipelines/alpine:latest": rpc error: code = Unknown desc = reading manifest latest in registry.gitlab.com/privatepath/alpine: errors: denied: requested access to the resource is denied unauthorized: authentication required

How / Where do I add authentication for my private registry?