code: def format_endpoint(schema, addr, port, api_version):
      
      return '{}://{}:{}/{}/'.format(schema, addr, port,
                                     get_api_suffix(api_version))
docs: Return a formatted keystone endpoint
      @param schema: http or https
      @param addr: ipv4/ipv6 host of the keystone service
      @param port: port of the keystone service
      @param api_version: 2 or 3
      @returns a fully formatted keystone endpoint