Unicode error when attach a non-english file.

[bear0330]

If I attach a file named: 抽獎系統工時預估.xlsx
I got this error:

Traceback (most recent call last):
  File "C:\Python27\lib\site-packages\trac\web\main.py", line 551, in _dispatch_request
    dispatcher.dispatch(req)
  File "C:\Python27\lib\site-packages\trac\web\main.py", line 244, in dispatch
    resp = chosen_handler.process_request(req)
  File "C:\Python27\lib\site-packages\trac\attachment.py", line 529, in process_request
    data = self._do_save(req, attachment)
  File "C:\Python27\lib\site-packages\trac\attachment.py", line 782, in _do_save
    attachment.insert(filename, upload.file, size)
  File "C:\Python27\lib\site-packages\trac\attachment.py", line 345, in insert
    listener.attachment_added(self)
  File "build\bdist.win-amd64\egg\code_comments\subscription.py", line 413, in attachment_added
    Subscription.from_attachment(self.env, attachment)
  File "build\bdist.win-amd64\egg\code_comments\subscription.py", line 198, in from_attachment
    attachment.filename)
UnicodeEncodeError: 'ascii' codec can't encode characters in position 0-7: ordinal not in range(128)