Python 3.13 removed the deprecated "cgi" module (see https://docs.python.org/3.12/library/cgi.html), but the latest released version 2.1.0 of formencode still uses the "cgi" module.

That leads to an ImportError for any users of formencode on Python 3.13:

/opt/hostedtoolcache/Python/3.13.0-rc.1/x64/lib/python3.13/site-packages/formencode/validators.py:8: in <module>
    import cgi
E   ModuleNotFoundError: No module named 'cgi'

PR #176 fixed that, but is not yet in a released version of formencode. Since Python 3.13.0 will be GA in the next couple of weeks, a new version of formencode with that fix should be released.