I notice that Nevow is now available from pypi.org, but has a syntax error when imported:

Python 3.6.8 (default, Nov 16 2020, 16:55:22) 
[GCC 4.8.5 20150623 (Red Hat 4.8.5-44)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import nevow
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/runbench3.6/lib/python3.6/site-packages/nevow/__init__.py", line 73, in <module>
    from nevow import flat
  File "/usr/local/runbench3.6/lib/python3.6/site-packages/nevow/flat/__init__.py", line 7, in <module>
    from nevow.flat.ten import flatten, precompile, iterflatten, getSerializer, serialize, registerFlattener, getFlattener, partialflatten
  File "/usr/local/runbench3.6/lib/python3.6/site-packages/nevow/flat/ten.py", line 13, in <module>
    from nevow import tags
  File "/usr/local/runbench3.6/lib/python3.6/site-packages/nevow/tags.py", line 28, in <module>
    from nevow.stan import Proto, Tag, directive, raw, xml, CommentProto, invisible, slot, cdata
  File "/usr/local/runbench3.6/lib/python3.6/site-packages/nevow/stan.py", line 150
    raise NotImplementedError, "Stan slot instances are not iterable."
SyntaxError: invalid syntax

That isn't valid Python 3, so how come Nevow is installable?
Are there any plans to fix it?