Cannot find module 'babel-runtime'

Problem described [here](https://github.com/rollup/rollup/issues/1141) and [here](https://github.com/rollup/rollup/issues/1141).
It seems [`babel-preset-es2015-rollup`](https://github.com/rollup/babel-preset-es2015-rollup) you used is not maintained any more.

# Way to fix
Replace the lib with [`babel-plugin-external-helpers`](http://babeljs.io/docs/plugins/external-helpers/)
and add this to package.json:
```
{
"presets": [
["es2015", { "modules": false }]
],
"plugins": [
"external-helpers"
]
}
```

---
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Start by inspecting package.json and the Babel configuration, then reproduce the missing babel-runtime error described in the linked Rollup issues. Replace the unmaintained Babel preset as proposed, configure external helpers, and verify that the project no longer fails to resolve babel-runtime.

Written by the indexing model from the issue text.