Cannot attach files with size smaller than 1001 bytes.

[mailxbox2@…]

Try to attach file disclosed to this ticket. It has exactly 1001 bytes and everything will be ok. But if you delete at least one character, file size will drop below magic 1001 bytes and attaching it to wiki page will end with such traceback:

Traceback (most recent call last):
  File "/var/lib/python-support/python2.5/trac/web/main.py", line 387, in dispatch_request
    dispatcher.dispatch(req)
  File "/var/lib/python-support/python2.5/trac/web/main.py", line 237, in dispatch
    resp = chosen_handler.process_request(req)
  File "/var/lib/python-support/python2.5/trac/attachment.py", line 361, in process_request
    self._do_save(req, attachment)
  File "/var/lib/python-support/python2.5/trac/attachment.py", line 450, in _do_save
    size = upload.file.len
AttributeError: 'cStringIO.StringO' object has no attribute 'len'

[Emmanuel Blot]

Submitted twice (#5297)