Hi, I've been following tutorial https://doc.nuxeo.com/nxdoc/develop-with-nuxeo-platform/ But when I try to export the contributions I keep getting this error. What does it mean and how can I fix it? Thanks

- Working... It can take some time, please be patient.events.js:174
      throw er; // Unhandled 'error' event
      ^

Error: spawn mvn ENOENT
    at Process.ChildProcess._handle.onexit (internal/child_process.js:240:19)
    at onErrorNT (internal/child_process.js:415:16)
    at process._tickCallback (internal/process/next_tick.js:63:19)
Emitted 'error' event at:
    at Process.ChildProcess._handle.onexit (internal/child_process.js:246:12)
    at process._tickCallback (internal/process/next_tick.js:63:19)