Configuration error leads to very ugly error

[PBruin]

After upgrading to the latest version I got a very ugly error:

Traceback (most recent call last):
  File "c:\python23\Lib\site-packages\trac\web\modpython_frontend.py", line 265, in handler
    dispatch_request(mpr.path_info, mpr, env)
  File "c:\python23\Lib\site-packages\trac\web\main.py", line 423, in dispatch_request
    dispatcher.dispatch(req)
  File "c:\python23\Lib\site-packages\trac\web\main.py", line 285, in dispatch
    resp = chosen_handler.process_request(req)
  File "c:\python23\Lib\site-packages\trac\attachment.py", line 255, in process_request
    self._do_save(req, attachment)
  File "c:\python23\Lib\site-packages\trac\attachment.py", line 302, in _do_save
    attachment.insert(filename, upload.file, size)
  File "c:\python23\Lib\site-packages\trac\attachment.py", line 125, in insert
    assert commonprefix == attachments_dir
AssertionError

After some digging I found it was caused by the following configuration error:
PythonOption TracEnv "c:/trac_dir/trac.db" instead of
PythonOption TracEnv "c:\trac_dir\trac.db"

I think a nice TracError with a usefull message would save people some time. Ofcourse the ability to handle both formats would even be nicer.

[Matthew Good]

This looks like a duplicate of #1705.

[Christian Boos]

(clearing report:35)