async fileResponse(path) {
    // Get file content
    let data;
    try {
      data = await this.readFile(path);
    } catch (e) {
      return this.notFound();
    }

    return { text: data };
  }
Creates a response with file content.
@param {String} path The path of the file to return.
@returns {Object} The PromiseRouter response.