code: function readLines(path, callback) {
      return new Promise(function(resolve, reject) {
          const stream = fsExtra.createReadStream(path);
          stream.on('error', reject);
          stream.on('end', resolve);
  
          const lineReader = readline.createInterface({
              input : stream
          });
          lineReader.on('line', callback);
      });
  }
docs: Read a file line-by-line.
  
  @param {String} path Path to the file.
  @param {Function} callback Function to call when reading each line.
  @returns {Promise} A promise when the reader is finished.
  
  @private