old_contents: const rollup = require('rollup')
  const babel = require('rollup-plugin-babel')
  
  rollup
    .rollup({
      entry: 'src/index.js',
      external: id =>
        /ramda/.test(id) || ['sinon', 'fluent-arguments'].includes(id),
      plugins: [
        babel({
          presets: [['latest', { es2015: { modules: false, loose: true } }]],
          plugins: ['ramda', 'external-helpers']
        })
      ]
    })
    .then(bundle => {
      bundle.write({
        dest: 'dist/index.js',
        format: 'cjs'
      })
      bundle.write({
        dest: 'dist/index.mjs',
        format: 'es'
      })
    })
  
new_contents: const rollup = require('rollup')
  const babel = require('rollup-plugin-babel')
  
  rollup
    .rollup({
      entry: 'src/index.js',
      external: id =>
        /ramda/.test(id) || ['sinon', 'fluent-arguments'].indexOf(id) >= 0,
      plugins: [
        babel({
          presets: [['latest', { es2015: { modules: false, loose: true } }]],
          plugins: ['ramda', 'external-helpers']
        })
      ]
    })
    .then(bundle => {
      bundle.write({
        dest: 'dist/index.js',
        format: 'cjs'
      })
      bundle.write({
        dest: 'dist/index.mjs',
        format: 'es'
      })
    })
  
subject: Make build script more compatible