urllib issue urllib.error.HTTPError: HTTP Error 503: Service Unavailable

[FischerJo]

I just installed the dependencies and tried to run the example

python3 main.py --prune_type=lt --arch_type=fc1 --dataset=mnist --prune_percent=10 --prune_iterations=35

and got the following error

Downloading http://yann.lecun.com/exdb/mnist/train-images-idx3-ubyte.gz to ../data/MNIST/raw/train-images-idx3-ubyte.gz
Traceback (most recent call last):
  File "main.py", line 427, in <module>
    main(args, ITE=1)
  File "main.py", line 39, in main
    traindataset = datasets.MNIST('../data', train=True, download=True,transform=transform)
  File "/home/fischer/miniconda3/lib/python3.8/site-packages/torchvision/datasets/mnist.py", line 79, in __init__
    self.download()
  File "/home/fischer/miniconda3/lib/python3.8/site-packages/torchvision/datasets/mnist.py", line 146, in download
    download_and_extract_archive(url, download_root=self.raw_folder, filename=filename, md5=md5)
  File "/home/fischer/miniconda3/lib/python3.8/site-packages/torchvision/datasets/utils.py", line 314, in download_and_extract_archive
    download_url(url, download_root, filename, md5)
  File "/home/fischer/miniconda3/lib/python3.8/site-packages/torchvision/datasets/utils.py", line 140, in download_url
    raise e
  File "/home/fischer/miniconda3/lib/python3.8/site-packages/torchvision/datasets/utils.py", line 132, in download_url
    _urlretrieve(url, fpath)
  File "/home/fischer/miniconda3/lib/python3.8/site-packages/torchvision/datasets/utils.py", line 29, in _urlretrieve
    with urllib.request.urlopen(urllib.request.Request(url, headers={"User-Agent": USER_AGENT})) as response:
  File "/home/fischer/miniconda3/lib/python3.8/urllib/request.py", line 222, in urlopen
    return opener.open(url, data, timeout)
  File "/home/fischer/miniconda3/lib/python3.8/urllib/request.py", line 531, in open
    response = meth(req, response)
  File "/home/fischer/miniconda3/lib/python3.8/urllib/request.py", line 640, in http_response
    response = self.parent.error(
  File "/home/fischer/miniconda3/lib/python3.8/urllib/request.py", line 569, in error
    return self._call_chain(*args)
  File "/home/fischer/miniconda3/lib/python3.8/urllib/request.py", line 502, in _call_chain
    result = func(*args)
  File "/home/fischer/miniconda3/lib/python3.8/urllib/request.py", line 649, in http_error_default
    raise HTTPError(req.full_url, code, msg, hdrs, fp)
urllib.error.HTTPError: HTTP Error 503: Service Unavailable

My guess is that the side somehow blocks the request (blocks python script requests, requires captcha solving,...), as a google search revealed similar issues with this library.
Is there any workaround?