Slicer fails to download custom sample data

Development
,
10

Could you try the following ?

The snippet is expected to work in both PythonSlicer and a regular python interpreter.

import sys
import traceback
import urllib.request


def processEvents():
    try:
        import slicer
        slicer.app.processEvents()
    except (AttributeError, ImportError):
        pass

    
def display(text, file=sys.stdout):
    processEvents()
    print(text, flush=True, file=file)

    
def error(text):
    display(text, file=sys.stderr)


for url, expected_success in [
    ("https://data.kitware.com", True),
    ("https://www.httpvshttps.com/", True),
    ("https://slicer.org/", True),
    ("https://expired.badssl.com/", False),
    ("https://github.com/", True),
]:
    display("-" * 8)
    display(f"Checking {url}")
    try:
        with urllib.request.urlopen(url) as response:
           data = response.read()
           html = data.decode('utf8')
           assert "<head>" in html[:600]
        if expected_success:
            display(f"Checking {url} - OK")
        else:
            error(f"Checking {url} - FAILED - should have raised an exception")
    except Exception as exc:
        if expected_success:
            error(f"Checking {url} - FAILED - unexpected exception")
            traceback.print_exc()
        else:
            display(f"Checking {url} - OK  [Expected {exc}]")

Expected output:

--------
Checking https://data.kitware.com
Checking https://data.kitware.com - ok
--------
Checking https://www.httpvshttps.com/
Checking https://www.httpvshttps.com/ - ok
--------
Checking https://slicer.org/
Checking https://slicer.org/ - ok
--------
Checking https://expired.badssl.com/
Checking https://expired.badssl.com/ - ok  [Expected <urlopen error [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: certificate has expired (_ssl.c:1129)>]
--------
Checking https://github.com/
Checking https://github.com/ - OK