ERROR: 'NoneType' object is not callable

[anonymous]

I've been getting the following error on and off today when attempting to view the Build Status page. It seems to appear for about half an hour, and then suddenly everything returns to normal. The result is the same for authenticated and anonymous users

2008-03-17 15:10:41,958 Trac[main] ERROR: 'NoneType' object is not callable
Traceback (most recent call last):
  File "/usr/lib/python2.4/site-packages/Trac-0.11b2-py2.4.egg/trac/web/main.py", line 419, in _dispatch_request
    dispatcher.dispatch(req)
  File "/usr/lib/python2.4/site-packages/Trac-0.11b2-py2.4.egg/trac/web/main.py", line 196, in dispatch
    resp = chosen_handler.process_request(req)
  File "/usr/lib/python2.4/site-packages/Bitten-0.6dev_r521-py2.4.egg/bitten/web_ui.py", line 128, in process_request
    self._render_overview(req)
  File "/usr/lib/python2.4/site-packages/Bitten-0.6dev_r521-py2.4.egg/bitten/web_ui.py", line 166, in _render_overview
    req.hdf[prefix + '.youngest_rev'] = {
  File "/usr/lib/python2.4/site-packages/Trac-0.11b2-py2.4.egg/trac/wiki/formatter.py", line 1123, in wiki_to_oneliner
    OneLinerFormatter(env, context).format(wikitext, out, shorten)
  File "/usr/lib/python2.4/site-packages/Trac-0.11b2-py2.4.egg/trac/wiki/formatter.py", line 950, in format
    result = re.sub(self.wikiparser.rules, self.replace, result)
  File "/usr/lib/python2.4/sre.py", line 142, in sub
    return _compile(pattern, 0).sub(repl, string, count)
  File "/usr/lib/python2.4/site-packages/Trac-0.11b2-py2.4.egg/trac/wiki/formatter.py", line 804, in replace
    replacement = self.handle_match(fullmatch)
  File "/usr/lib/python2.4/site-packages/Trac-0.11b2-py2.4.egg/trac/wiki/formatter.py", line 797, in handle_match
    return external_handler(self, match, fullmatch)
  File "/usr/lib/python2.4/site-packages/Trac-0.11b2-py2.4.egg/trac/wiki/api.py", line 291, in wikipagename_link
    self.ignore_missing_pages)
  File "/usr/lib/python2.4/site-packages/Trac-0.11b2-py2.4.egg/trac/wiki/api.py", line 325, in _format_link
    if 'WIKI_VIEW' in formatter.perm('wiki', pagename, version):

[cmlenz]

Also filed as #259.