docs: function ensureActiveTheme(req, res, next) {
      // CASE: this means that the theme hasn't been loaded yet i.e. there is no active theme
      if (!activeTheme.get()) {
          // This is the one place we ACTUALLY throw an error for a missing theme as it's a request we cannot serve
          return next(new common.errors.InternalServerError({
              // We use the settingsCache here, because the setting will be set,
              // even if the theme itself is not usable because it is invalid or missing.
              message: common.i18n.t('errors.middleware.themehandler.missingTheme', {theme: settingsCache.get('active_theme')})
          }));
      }
  
      // CASE: bootstrap theme validation failed, we would like to show the errors on the blog [only production]
      if (activeTheme.get().error && config.get('env') === 'production') {
          return next(new common.errors.InternalServerError({
              // We use the settingsCache here, because the setting will be set,
              // even if the theme itself is not usable because it is invalid or missing.
              message: common.i18n.t('errors.middleware.themehandler.invalidTheme', {theme: settingsCache.get('active_theme')}),
              errorDetails: activeTheme.get().error.errorDetails
          }));
      }
  
      // If the active theme has not yet been mounted, mount it into express
      if (!activeTheme.get().mounted) {
          activeTheme.get().mount(req.app);
      }
  
      next();
  }