How can i get the error response if upload fails?
currently it get the error respond and convert it to string, how can i get the originally error respond object?

ElementUI upload component
<el-upload
            class="upload-demo"
            ref="upload"
            action="http://localhost:8000/api/files"
            :headers="headers"
            :auto-upload="false"
            :on-success="handleUploadSuccess"
            :on-error="handleUploadError"
>

handleUploadError(err, file){
      console.log(err); //its a string of the server respond instead of the respond object
}