setup.py uses ast.Str, which was removed in Python 3.14. As a result, attempting to build or install html5lib under Python 3.14 fails with an AttributeError, similar to below:

 > File "setup.py", line 93, in <module>
 > isinstance(a.value, ast.Str)):
 > ^^^^^^^
 > AttributeError: module 'ast' has no attribute 'Str'