Can't attach file to ticket in Trac

As mentioned in #macports: When trying to attach a file to a ticket,  
I recieved this familiar traceback:

Traceback (most recent call last):
   File "/Library/Frameworks/Python.framework/Versions/2.4/lib/ 
python2.4/site-packages/trac/web/modpython_frontend.py", line 209, in  
handler
     dispatch_request(mpr.path_info, mpr, env)
   File "/Library/Frameworks/Python.framework/Versions/2.4/lib/ 
python2.4/site-packages/trac/web/main.py", line 139, in dispatch_request
     dispatcher.dispatch(req)
   File "/Library/Frameworks/Python.framework/Versions/2.4/lib/ 
python2.4/site-packages/trac/web/main.py", line 107, in dispatch
     resp = chosen_handler.process_request(req)
   File "/Library/Frameworks/Python.framework/Versions/2.4/lib/ 
python2.4/site-packages/trac/attachment.py", line 267, in  
process_request
     self._do_save(req, attachment)
   File "/Library/Frameworks/Python.framework/Versions/2.4/lib/ 
python2.4/site-packages/trac/attachment.py", line 335, in _do_save
     attachment.insert(filename, upload.file, size)
   File "/Library/Frameworks/Python.framework/Versions/2.4/lib/ 
python2.4/site-packages/trac/attachment.py", line 142, in insert
     os.makedirs(self.path)
   File "/Library/Frameworks/Python.framework/Versions/2.4/lib/ 
python2.4/os.py", line 159, in makedirs
     mkdir(name, mode)
OSError: [Errno 13] Permission denied: '/trac/env/macports/ 
attachments/ticket/10646'

- Daniel