LookupError: unknown encoding: X-UNKNOWN

It's quite unpleasant to recieve this mail daily. In
addition there was a local mailing list to which no mail was
delivered until digests to this list was turned off.

Last day I have upgraded to mailman 2.1.3 and the last lines
of the traceback changed:

  File "/usr/local/mailman/pythonlib/email/Message.py", line
714, in get_filename
    return unicode(newvalue[2], newvalue[0] or 'us-ascii')
LookupError: unknown encoding: X-UNKNOWN

Hello,

I have the same problem with mailmain-2.1.4 with
python-2.3.3 under linux gentoo. Are there any clues where
the problem lies or any workarounds? Disableing the digest
option works but is not really a solution.
Another interesting fact is, that the only some lists show
this problem and that the prolbem just "occurs" and then it
doesn't go away..

Here's a part of my error log:
Apr 26 18:27:05 2004 (17449) Uncaught runner exception:
unknown encoding: X-UNKNOWN
Apr 26 18:27:05 2004 (17449) Traceback (most recent call last):
  File "/usr/local/mailman/Mailman/Queue/Runner.py", line
110, in _oneloop
    self._onefile(msg, msgdata)
  File "/usr/local/mailman/Mailman/Queue/Runner.py", line
160, in _onefile
    keepqueued = self._dispose(mlist, msg, msgdata)
  File "/usr/local/mailman/Mailman/Queue/IncomingRunner.py",
line 130, in _dispose
    more = self._dopipeline(mlist, msg, msgdata, pipeline)
  File "/usr/local/mailman/Mailman/Queue/IncomingRunner.py",
line 153, in _dopipeline
    sys.modules[modname].process(mlist, msg, msgdata)
  File "/usr/local/mailman/Mailman/Handlers/ToDigest.py",
line 91, in process
    send_digests(mlist, mboxfp)
  File "/usr/local/mailman/Mailman/Handlers/ToDigest.py",
line 132, in send_digests
    send_i18n_digests(mlist, mboxfp)
  File "/usr/local/mailman/Mailman/Handlers/ToDigest.py",
line 306, in send_i18n_digests
    msg = scrubber(mlist, msg)
  File "/usr/local/mailman/Mailman/Handlers/Scrubber.py",
line 265, in process
    url = save_attachment(mlist, part, dir)
  File "/usr/local/mailman/Mailman/Handlers/Scrubber.py",
line 361, in save_attachment
    fnext = os.path.splitext(msg.get_filename(''))[1]
  File "/usr/local/mailman/pythonlib/email/Message.py", line
714, in get_filename
    return unicode(newvalue[2], newvalue[0] or 'us-ascii')
LookupError: unknown encoding: X-UNKNOWN

Apr 26 18:27:05 2004 (17449) SHUNTING:
1082996756.746207+e85fdb8b141ccd2a8f0757824f62fbff58
da2ce4

As far as I recognised mailman copies Message.py from the
python libraries so I also reported it for python (id 854102).

As a workaround replace the line in question:

return unicode(newvalue[2], newvalue[0] or 'us-ascii')

with

try:
  return unicode(newvalue[2], newvalue[0] or 'us-ascii')
except LookupError:
  return unicode(newvalue[2], 'us-ascii', 'replace')