function isPackagerRunning(packagerPort = (process.env.RCT_METRO_PORT || 8081)) {
  return fetch(`http://localhost:${packagerPort}/status`).then(
    res => res.text().then(body =>
      body === 'packager-status:running' ? 'running' : 'unrecognized'
    ),
    () => 'not_running'
  );
}
Indicates whether or not the packager is running. It returns a promise that
when fulfilled can returns one out of these possible values:
  - `running`: the packager is running
  - `not_running`: the packager nor any process is running on the expected
                   port.
  - `unrecognized`: one other process is running on the port we expect the
                    packager to be running.