[TurboGears] master.kidをいじると、"TypeError: 'NoneType' object is not callable"が発生する、ことがある。

環境

この記事の内容は、TurboGears 1.0.1で確認しました。

現象

master.kidを書き換えると、以下のエラーが発生します。

500 Internal error

The server encountered an unexpected condition which prevented it from fulfilling the request.

Page handler: >
Traceback (most recent call last):
  File "/usr/lib/python2.4/site-packages/CherryPy-2.2.1-py2.4.egg/cherrypy/_cphttptools.py", line 105, in _run
    self.main()
  File "/usr/lib/python2.4/site-packages/CherryPy-2.2.1-py2.4.egg/cherrypy/_cphttptools.py", line 254, in main
    body = page_handler(*virtual_path, **self.params)
  File "", line 3, in index
  File "/usr/lib/python2.4/site-packages/TurboGears-1.0.1-py2.4.egg/turbogears/controllers.py", line 334, in expose
    output = database.run_with_transaction(
  File "", line 5, in run_with_transaction
  File "/usr/lib/python2.4/site-packages/TurboGears-1.0.1-py2.4.egg/turbogears/database.py", line 302, in so_rwt
    retval = func(*args, **kw)
  File "", line 5, in _expose
  File "/usr/lib/python2.4/site-packages/TurboGears-1.0.1-py2.4.egg/turbogears/controllers.py", line 351, in 
    mapping, fragment, args, kw)))
  File "/usr/lib/python2.4/site-packages/TurboGears-1.0.1-py2.4.egg/turbogears/controllers.py", line 391, in _execute_func
    return _process_output(output, template, format, content_type, mapping, fragment)
  File "/usr/lib/python2.4/site-packages/TurboGears-1.0.1-py2.4.egg/turbogears/controllers.py", line 82, in _process_output
    fragment=fragment)
  File "/usr/lib/python2.4/site-packages/TurboGears-1.0.1-py2.4.egg/turbogears/view/base.py", line 131, in render
    return engine.render(**kw)
  File "/usr/lib/python2.4/site-packages/TurboKid-0.9.8-py2.4.egg/turbokid/kidsupport.py", line 156, in render
    return t.serialize(encoding=self.defaultencoding, output=format, fragment=fragment)
  File "/usr/lib/python2.4/site-packages/kid-0.9.3-py2.4.egg/kid/__init__.py", line 236, in serialize
    return serializer.serialize(self, encoding, fragment)
  File "/usr/lib/python2.4/site-packages/kid-0.9.3-py2.4.egg/kid/serialization.py", line 51, in serialize
    text = list(self.generate(stream, encoding, fragment))
  File "/usr/lib/python2.4/site-packages/kid-0.9.3-py2.4.egg/kid/serialization.py", line 326, in generate
    stream = iter(stream)
  File "/usr/lib/python2.4/site-packages/kid-0.9.3-py2.4.egg/kid/__init__.py", line 261, in __iter__
    return iter(self.transform())
  File "/usr/lib/python2.4/site-packages/kid-0.9.3-py2.4.egg/kid/__init__.py", line 316, in transform
    stream = self.pull()
  File "/usr/lib/python2.4/site-packages/kid-0.9.3-py2.4.egg/kid/__init__.py", line 275, in pull
    self.initialize()
  File "/home/tom/projects/CalciumRider/car/templates/article/search/index.py", line 21, in initialize
  File "/home/tom/projects/CalciumRider/car/templates/master.py", line 21, in initialize
TypeError: 'NoneType' object is not callable

この現象の再現性は低く、発生するときとしないときがあります。

原因

分かりません。

詳細

ときを改めて、以下のRubyスクリプトを実行して、エラーが発生したURLを10000回リクエストし、エラーが発生する回数を計測してみました。

# ruby

require "open-uri"

count = 0
10000.times do 
  open("http://127.0.0.1:8080/article/list") do |f|
    if 0 < f.grep(/Internal error/).size()
      count += 1
    end
  end
end

puts count

# vim: tabstop=2 shiftwidth=2 expandtab

結果は、0でした（1回もエラーにならなかった）。原因がはっきりしないまま、発生しなくなりました。

所感

一体、なんだったんだろう...。