docs: def get_container_version():
      """Return the version of the docker container running the present server,
      or '' if not in a container"""
      root_dir = os.path.dirname(os.path.realpath(sys.argv[0]))
      version_file = os.path.join(root_dir, 'VERSION')
      if os.path.exists(version_file):
          with open(version_file) as f:
              return f.read()
      return ''