Error deleting pages with spaces in title when using AutoWikify

[rileypb@…]

Note: I'm assuming this is a bug with AutoWikify because the error crops up in that code. If this is not the case, let me know and I'll refile as a Trac defect.

• in wiki with TRAC_ADMIN privileges
• attempted to delete page titled 'Test This'
• got this error:

Traceback (most recent call last):
  File "C:\PROGRA~1\Python\Lib\site-packages\trac\web\cgi_frontend.py", line 130, in run
    dispatch_request(req.path_info, req, env)
  File "C:\PROGRA~1\Python\Lib\site-packages\trac\web\main.py", line 139, in dispatch_request
    dispatcher.dispatch(req)
  File "C:\PROGRA~1\Python\Lib\site-packages\trac\web\main.py", line 107, in dispatch
    resp = chosen_handler.process_request(req)
  File "C:\PROGRA~1\Python\Lib\site-packages\trac\wiki\web_ui.py", line 96, in process_request
    self._do_delete(req, db, page)
  File "C:\PROGRA~1\Python\Lib\site-packages\trac\wiki\web_ui.py", line 164, in _do_delete
    page.delete(version, db)
  File "C:\PROGRA~1\Python\Lib\site-packages\trac\wiki\model.py", line 98, in delete
    listener.wiki_page_deleted(self)
  File "build\bdist.win32\egg\tracautowikify\autowikify.py", line 32, in wiki_page_deleted
  File "C:\Program Files\Python\lib\sets.py", line 534, in remove
    del self._data[element]
KeyError: 'Test This'

[Alec Thomas]

(In [736]) Fixes #351