docs: def fetch(url, fullpath):
      '''
      Fetch data from an URL and save it under the given target name.
      '''
      logger.debug("Fetching %s from %s" % (fullpath, url))
  
      try:
          tmpfile, headers = urlretrieve(url)
          if os.path.exists(fullpath):
              os.remove(fullpath)
          shutil.move(tmpfile, fullpath)
      except Exception as e:
          logger.error("Error during fetching: " + str(e))
          raise