code: def log_in_to_required_registries():
      
      registries = set()
      specs = spec_assembler.get_assembled_specs()
      for spec in specs.get_apps_and_services():
          if 'image' in spec and spec.get('image_requires_login'):
              registries.add(registry_from_image(spec['image']))
      unauthed_registries = registries.difference(get_authed_registries())
      for registry in unauthed_registries:
          log_in_to_registry(registry)
docs: Client-side command which runs the user through a login flow
      (via the Docker command-line client so auth is persisted)
      for any registries of active images which require a login. This
      is based on the `image_requires_login` key in the individual specs.