docs: def getContainerByTag(tag):
      '''Check if a container with a given tag exists. No side-effects.
      Idempotent. Handles NotFound and APIError exceptions, but only reraises
      APIError. Returns None if the container is not found. Otherwise, returns the
      container.'''
      require_str("tag", tag)
  
      container = None
      try:
          container = client.containers.get(tag)
          print("Found container", tag, "...")
      except NotFound:
          #print("Container", tag, "does not exist ...")
          pass
      except APIError as exc:
          eprint("Unhandled error while getting container", tag)
          raise exc
  
      return container