test/unit/remote: Return Chromium error from fetch
test/unit/remote: Return Chromium error from fetch

  To test the behavior of the client Desktop when encountering the
  cryptic error `mojo result is not ok`, we stubbed the `cozy-client-js`
  we call so it would throw the error.

  However, this pushes us away from the actual client behavior and
  prevents us from testing other cases like content length mismatch
  between the `Content-Length` header and the actual data sent since we
  would not consume the readable stream at all.

  We created a new stub that actually reads data and thus consumes the
  input stream and fires `data` events while still throwing the Chromium
  error at the end.

cozy-labs/cozy-desktop,cozy-labs/cozy-desktop,cozy-labs/cozy-desktop,cozy-labs/cozy-desktop