text: const fs = require('fs')
  
  function exists (fn, cb) {
    fs.stat(fn, (err, stat) => {
      if (err) {
        return cb(err)
      }
      if (!stat.isFile()) {
        const err = new Error(`${fn} is not a file`)
        return cb(err)
      }
      cb()
    })
  }
  
  module.exports = exists
  