code: func readConfig(siteRoot string) (installationSiteConfig, error) {
  	path := filepath.Join(siteRoot, fs.SiteServiceDir, "config.json")
  	c := installationSiteConfig{}
  	if err := c.read(path); err != nil && !os.IsNotExist(err) {
  		return c, err
  	}
  	return c, nil
  }
docs: // readConfig reads config, returning default one if missing.
  //
  // The returned config may have ServiceURL set to "" due to previous buggy
  // version of CIPD not setting it up correctly.