wiki moinmoin1.9.7 一个问题，用户登录后任何预览都要出错，不知何因。

wiki moinmoin1.9.7 一个问题，用户登录后任何预览（即使不修改内容）都要出错,如下：

The server encountered an internal error and was unable to complete your request.  Either the server is overloaded or there is an error in the application.

如果没有用户登录，修改、预览没有任何问题。

试了WINDOWS , UBUNTU12.04作服务器，都一样。 moinmoin 服务器端提示如下：

2014-01-01 16:14:11,673 INFO MoinMoin.web.serving:41 192.168.0.138 "GET /moin_static197/modern/img/moin-conflict.png HTTP/1.1" 200 -
2014-01-01 16:14:13,990 INFO MoinMoin.web.serving:41 192.168.0.138 "GET /DOS%E5%9C%A8%E8%BF%99%E9%87%8C HTTP/1.1" 200 -
2014-01-01 16:14:29,002 INFO MoinMoin.web.serving:41 192.168.0.138 "GET /DOS%E5%9C%A8%E8%BF%99%E9%87%8C?action=edit&editor=text HTTP/1.1" 200 -
2014-01-01 16:14:35,645 ERROR MoinMoin.wsgiapp:293 An exception has occurred [http://192.168.0.88:8080/DOS%E5%9C%A8%E8%BF%99%E9%87%8C].
Traceback (most recent call last):
  File "/home/samxiao/moin-1.9.7/MoinMoin/wsgiapp.py", line 282, in __call__
    response = run(context)
  File "/home/samxiao/moin-1.9.7/MoinMoin/wsgiapp.py", line 88, in run
    response = dispatch(request, context, action_name)
  File "/home/samxiao/moin-1.9.7/MoinMoin/wsgiapp.py", line 136, in dispatch
    response = handle_action(context, pagename, action_name)
  File "/home/samxiao/moin-1.9.7/MoinMoin/wsgiapp.py", line 195, in handle_action
    handler(context.page.page_name, context)
  File "/home/samxiao/moin-1.9.7/MoinMoin/action/edit.py", line 152, in execute
    pg.sendEditor(preview=savetext, comment=comment)
  File "/home/samxiao/moin-1.9.7/MoinMoin/PageEditor.py", line 296, in sendEditor
    self._save_draft(raw_body, rev)
  File "/home/samxiao/moin-1.9.7/MoinMoin/PageEditor.py", line 856, in _save_draft
    cache_data = cache.content()
  File "/home/samxiao/moin-1.9.7/MoinMoin/caching.py", line 285, in content
    raise CacheError(str(err))
CacheError
2014-01-01 16:14:35,666 INFO MoinMoin.web.serving:41 192.168.0.138 "POST /DOS%E5%9C%A8%E8%BF%99%E9%87%8C HTTP/1.1" 500 -
2014-01-01 16:14:35,694 ERROR werkzeug:116 Error on request:
Traceback (most recent call last):
  File "/home/samxiao/moin-1.9.7/MoinMoin/support/werkzeug/serving.py", line 159, in run_wsgi
    execute(app)
  File "/home/samxiao/moin-1.9.7/MoinMoin/support/werkzeug/serving.py", line 146, in execute
    application_iter = app(environ, start_response)
  File "/home/samxiao/moin-1.9.7/MoinMoin/support/werkzeug/wsgi.py", line 411, in __call__
    return self.app(environ, start_response)
  File "/home/samxiao/moin-1.9.7/MoinMoin/wsgiapp.py", line 282, in __call__
    response = run(context)
  File "/home/samxiao/moin-1.9.7/MoinMoin/wsgiapp.py", line 88, in run
    response = dispatch(request, context, action_name)
  File "/home/samxiao/moin-1.9.7/MoinMoin/wsgiapp.py", line 136, in dispatch
    response = handle_action(context, pagename, action_name)
  File "/home/samxiao/moin-1.9.7/MoinMoin/wsgiapp.py", line 195, in handle_action
    handler(context.page.page_name, context)
  File "/home/samxiao/moin-1.9.7/MoinMoin/action/edit.py", line 152, in execute
    pg.sendEditor(preview=savetext, comment=comment)
  File "/home/samxiao/moin-1.9.7/MoinMoin/PageEditor.py", line 296, in sendEditor
    self._save_draft(raw_body, rev)
  File "/home/samxiao/moin-1.9.7/MoinMoin/PageEditor.py", line 856, in _save_draft
    cache_data = cache.content()
  File "/home/samxiao/moin-1.9.7/MoinMoin/caching.py", line 285, in content
    raise CacheError(str(err))
CacheError

新注册一个用户，编缉同一个页面，就没问题。奇怪啊！