I've found a bug.

Hi all.
Maybe it is kind of old bug, but it is extremely annoing me. I've got 
maximum recursion depth exceeded when I 've tried to build deep tree of 
rend.Fragment's.
Please take a look on this simpliest script (in reality i have much more 
complicated page).

#!/usr/bin/env python
# coding: utf-8
from zope.interface import Interface
from twisted.python.components import registerAdapter
from twisted.internet import task
from twisted.python import log, util
from twisted.internet import reactor
from nevow import rend, loaders, static, inevow, url, tags as T

class Border(rend.Fragment):
    docFactory = 
loaders.stan(T.table[T.tr[T.td(render=T.directive("content"))]])
    def __init__(self, content, *args, **kwargs):
        rend.Fragment.__init__(self, *args, **kwargs)
        self.content=content
    def render_content(self, context, data):
        return context.tag[self.content]


class BasePage(rend.Page):
    docFactory = loaders.stan(T.html[T.body(render=T.directive("content"))])
    def render_content(self, context, data):
        
self.content=Border(Border(Border(Border(Border(Border(Border(Border(Border(Border(Border(Border("Hello 
World"))))))))))))
        return context.tag[self.content]

if __name__ == '__main__':
    import sys
    from twisted.python import log
    from nevow import appserver

    page=BasePage()
    site=appserver.NevowSite(page)
    reactor.listenTCP(8080, site)
    reactor.run()

I hope that you help me to resolve this bug, or, at least, to avoid such 
situation.
Thanking before.

PS. I can't restructure my page.