code: def callback(self, request, **kwargs):
          
          try:
              client = self.get_evernote_client()
              # finally we save the user auth token
              # As we already stored the object ServicesActivated
              # from the UserServiceCreateView now we update the same
              # object to the database so :
              # 1) we get the previous object
              us = UserService.objects.get(user=request.user, name=ServicesActivated.objects.get(name='ServiceEvernote'))
              # 2) then get the token
              us.token = client.get_access_token(request.session['oauth_token'], request.session['oauth_token_secret'],
                                                 request.GET.get('oauth_verifier', ''))
              # 3) and save everything
              us.save()
          except KeyError:
              return '/'
  
          return 'evernote/callback.html'
docs: Called from the Service when the user accept to activate it