function getFileContentOrNull(filename) {
  return new Promise((resolve, reject) => {
    fs$3.readFile(filename, "utf8", (error, data) => {
      if (error && error.code !== "ENOENT") {
        reject(createError(filename, error));
      } else {
        resolve(error ? null : data);
      }
    });
  });
}
@param {string} filename
@returns {Promise<null | string>}