var a = fs.readFileSync('pla.txt');

var b = a
  .toString()
  .split(/^\n/gm)
  .map(x => x.split('\n'))
  .map(([file, ...errors]) => ({
    file,
    errors: errors.filter(err => err.includes('import/no-unused-modules')),
  }))
  .flatMap(err =>
    //                    filename    :    line number        ' '   identifier                               remove quotes
    err.errors.map(
      str => err.file + ':' + str.match(/\d+/) + ' ' + str.match(/(?!declaration )'(\w+)'/g)[0].slice(1, -1)
    )
  )
  .join('\n');

fs.writeFileSync('out.txt', b);