/**
  * @param ThemeInterface $theme
  * @param int $screenshotNumber
  *
  * @return string
  */
 private function getScreenshotPath(ThemeInterface $theme, $screenshotNumber)
 {
     $screenshots = $theme->getScreenshots();
     if (!isset($screenshots[$screenshotNumber])) {
         throw new NotFoundHttpException(sprintf('Theme "%s" does not have screenshot #%d', $theme->getTitle(), $screenshotNumber));
     }
     $screenshotRelativePath = $screenshots[$screenshotNumber];
     return rtrim($theme->getPath(), \DIRECTORY_SEPARATOR) . \DIRECTORY_SEPARATOR . $screenshotRelativePath;
 }