docs: function bundle () {
      var didError = false
      const outStream = fs.createWriteStream(outFile)
      const bStream = w.bundle()
  
      bStream.on('error', function (err) {
        console.error('[bundle]', String(err))
        didError = true
        outStream.end('console.error(' + JSON.stringify(String(err)) + ')')
      })
  
      // if we're not splitting vendor files, include them in the bundle
      if (!shouldSplitVendor && vendorFiles.length) {
        multistream(vendorFiles.map(createReadStream).concat(bStream))
          .pipe(outStream)
      } else {
        bStream.pipe(outStream)
      }
  
      outStream.on('error', function (err) {
        console.error('[bundle]', err)
      })
  
      outStream.on('close', function () {
        if (verbose && !didError) {
          // TODO: also display size of vendor files
          console.error(
            '[bundle] %d bytes written to %s (%s seconds)',
            bytes, outFile, (time / 1000).toFixed(2)
          )
        }
      })
    }