title: Flask-Uploads not generating url inside celery task
body: <p>Previously in my python flask application I was able to use </p>
  
  <blockquote>
    <p>photos.url("picture_name")</p>
  </blockquote>
  
  <p>without any issue. But after updating few libraries in my project, Celery is throwing exception </p>
  
  <blockquote>
    <p>RuntimeError: Application was not able to create a URL adapter for
    request independent URL generation. You might be able to fix this by
    setting the SERVER_NAME config variable.</p>
  </blockquote>
  
  <p>I don't have SERVER_NAME in my config but I don't need. It was working previously without this config so I am expecting it should even work now. Does anyone have any idea what am I missing?</p>