POST http://localhost:3000/photos/upload 401 (Unauthorized)

Ao realizar a atividade 11 da aula 01 do terceiro módulo do curso de Angular me deparei com o seguinte erro:

POST http://localhost:3000/photos/upload 401 (Unauthorized)

Isso acontece quando tento realizar o upload da imagem.

photo-form.component

import { PhotoService } from './../photo/photo.service';
import { FormBuilder, FormGroup, Validators } from '@angular/forms';
import { Component, OnInit } from '@angular/core';
import { Router } from '@angular/router';

@Component({
  // tslint:disable-next-line:component-selector
  selector: 'ap-photo-form',
  templateUrl: './photo-form.component.html',
  styleUrls: ['./photo-form.component.css']
})
export class PhotoFormComponent implements OnInit {

  photoForm: FormGroup;
  file: File;

  constructor(
    private formBuilder: FormBuilder,
    private photoService: PhotoService,
    private router: Router
  ) { }

  ngOnInit() {
    this.photoForm = this.formBuilder.group({
      file: ['', Validators.required],
      description: ['', Validators.maxLength(300)],
      allowComents: [true]
    });
  }

  upload() {
    const description = this.photoForm.get('description').value;
    const allowComents = this.photoForm.get('allowComents').value;

    this.photoService
      .upload(description, allowComents, this.file)
      .subscribe(() => this.router.navigate(['']));
  }

}

photo.component

import { Component, Input } from '@angular/core';

const CLOUD = 'http://localhost:3000/imgs/';

@Component({
    selector: 'ap-photo',
    templateUrl: 'photo.component.html'
})
export class PhotoComponent {

    private _url = '';

    @Input() description = '';

    @Input() set url(url: string) {

        if (!url.startsWith('data')) {
            this._url = CLOUD + url;
        } else {
            this._url = url;
        }
    }

    get url() {

        return this._url;
    }
}

Por que não esta autorizando? Poderiam me ajudar?