如何将Express中的错误返回到Promise中的前端?

I tried using a catch within the promise on client but it doesn't seem to pick up the error.

服务器:

pdf.create(pdfTemplate(transcriptAsObject), {}).toFile(`routes/api/${finalPdfName}`, (err) => {
  if(err) {
    res.send(Promise.reject());
  }

  res.send(Promise.resolve());
 });

客户:

axios.post('/create-pdf', this.state)
  .catch(err => console.log('error hit: ', err))
  .then(() => axios.get('fetch-pdf', { responseType: 'blob' }))
  .then((res) => {
    const pdfBlob = new Blob([res.data], { type: 'application/pdf' });
    saveAs(pdfBlob, 'newPdf.pdf');
  })
  .then(() => console.log('success brotha'))