Unable to load external file '../common/ext.css' because it's explicitly not allowed #50

WARN: std::wsyncbuf::wsyncbuf contains invalid link
WARN: std::wsyncbuf::~wsyncbuf contains invalid link
Processing file: 0/4424: output/reference_cssless/en/cpp.html
concurrent.futures.process._RemoteTraceback:.
"""
Traceback (most recent call last):
  File "/usr/lib/python3.13/concurrent/futures/process.py", line 254, in _process_worker
    r = call_item.fn(*call_item.args, **call_item.kwargs)
  File "/build/cppreference-doc-20250209/commands/preprocess_cssless.py", line 38, in preprocess_html_merge_cssless
    output = preprocess_html_merge_css(root, src_path)
  File "/build/cppreference-doc-20250209/commands/preprocess_cssless.py", line 77, in preprocess_html_merge_css
    root = premailer.transform().getroot()
           ~~~~~~~~~~~~~~~~~~~^^
  File "/usr/lib/python3/dist-packages/premailer/premailer.py", line 398, in transform
    css_body = self._load_external(href)
  File "/usr/lib/python3/dist-packages/premailer/premailer.py", line 589, in _load_external
    raise ExternalFileLoadingError(
    ...<2 lines>...
    )
premailer.premailer.ExternalFileLoadingError: Unable to load external file '../common/ext.css' because it's explicitly not allowed
"""

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/build/cppreference-doc-20250209/./preprocess_qch.py", line 75, in <module>
    main()
    ~~~~^^
  File "/build/cppreference-doc-20250209/./preprocess_qch.py", line 69, in main
    output = future.result()
  File "/usr/lib/python3.13/concurrent/futures/_base.py", line 449, in result
    return self.__get_result()
           ~~~~~~~~~~~~~~~~~^^
  File "/usr/lib/python3.13/concurrent/futures/_base.py", line 401, in __get_result
    raise self._exception
premailer.premailer.ExternalFileLoadingError: Unable to load external file '../common/ext.css' because it's explicitly not allowed

    $ find . -name ext.css
   ./tests/preprocess_cssless_data/ext.css