package-lock.json is out of date:
$ npm ci
npm ERR! cipm can only install packages when your package.json and package-lock.json or npm-shrinkwrap.json are in sync. Please update your lock file with `npm install` before continuing.
npm ERR!
npm ERR!
npm ERR! Invalid: lock file's react@15.6.2 does not satisfy react@^17.0.1
npm ERR! Invalid: lock file's react-dom@15.6.2 does not satisfy react-dom@^17.0.1
npm ERR!
Running npm install produces a large diff.