new_contents: import hashlib
  import os
  import requests
  import shutil
  
  
  # The tests files are located on sourceforge.
  def download_mesh(name, md5):
  
      filename = os.path.join('/tmp', name)
      if not os.path.exists(filename):
          print('Downloading %s...' % name)
          url = 'https://sourceforge.net/projects/meshzoo-data/files/'
          r = requests.get(url + name + '/download', stream=True)
          if not r.ok:
              raise RuntimeError(
                  'Download error (%s, return code %s).' % (r.url, r.status_code)
                  )
  
          # save the mesh in /tmp
          with open(filename, 'wb') as f:
              r.raw.decode_content = True
              shutil.copyfileobj(r.raw, f)
  
      # check MD5
      file_md5 = hashlib.md5(open(filename, 'rb').read()).hexdigest()
  
      if file_md5 != md5:
          raise RuntimeError(
              'Checksums not matching (%s != %s).' % (file_md5, md5)
              )
  
      return filename
  
subject: add fetch_data for tests