SpamDetect.py unable to process headers for ICS file

[Don Badrak]

I am running 2.1.16rc3. Since updating to this from 2.1.14, we are no longer able to send meeting invitations from Lotus Notes to Mailman lists.

I get this stack trace in the errors file:

Oct 23 10:11:04 2013 (5280) Uncaught runner exception:
Oct 23 10:11:04 2013 (5280) Traceback (most recent call last):
  File "/apps/mailman/Mailman/Queue/Runner.py", line 119, in _oneloop
    self._onefile(msg, msgdata)
  File "/apps/mailman/Mailman/Queue/Runner.py", line 190, in _onefile
    keepqueued = self._dispose(mlist, msg, msgdata)
  File "/apps/mailman/Mailman/Queue/IncomingRunner.py", line 130, in _dispose
    more = self._dopipeline(mlist, msg, msgdata, pipeline)
  File "/apps/mailman/Mailman/Queue/IncomingRunner.py", line 153, in _dopipeline
    sys.modules[modname].process(mlist, msg, msgdata)
  File "/apps/mailman/Mailman/Handlers/SpamDetect.py", line 99, in process
    headers += getDecodedHeaders(p, lcset)
  File "/apps/mailman/Mailman/Handlers/SpamDetect.py", line 71, in getDecodedHeaders
    v = decode_header(re.sub('\n\s', ' ', v))
  File "/usr/lib64/python2.6/email/header.py", line 101, in decode_header
    raise HeaderParseError
HeaderParseError

Oct 23 10:11:04 2013 (5280) SHUNTING: 1382537463.296186+6e41872d4cb789a2cb6b3439e6f6a4210cb32c3c

I have traced it down to this particular header:

X-Notes-Item: =?UTF-8?B?SW52aXRlIFJSW0xvY2FsXSBieSBIVFRQIFNlcnZlciBvbiBJVDAxMk1haWwo?=
 =?UTF-8?B?UmVsZWFzZSA4LjUuM0ZQM3xOb3ZlbWJlciAxNSwgMjAxMikgYXQgMTAvMjMv?=
 =?UTF-8?B?MjAxMyAwMjoyOTowNSBQTQ==?=,
        =?UTF-8?B?U2VuZFtMb2NhbF0gYnkgSFRUUCBTZXJ2ZXIgb24gSVQwMTJNYWlsKA==?=
 =?UTF-8?B?UmVsZWFzZSA4LjUuM0ZQM3xOb3ZlbWJlciAxNSwgMjAxMikgYXQgMTAvMjMv?=
 =?UTF-8?B?MjAxMyAwMjoyOTowNSBQTQ==?=,
        =?UTF-8?B?UHJlcGFyZVRvU2VuZFtMb2NhbF0gYnkgSFRUUCBTZXJ2ZXIgb24=?=
 =?UTF-8?B?IElUMDEyTWFpbChSZWxlYXNlIDguNS4zRlAzfE5vdmVtYmVyIDE1LCAyMDEy?=
 =?UTF-8?B?KSBhdCAxMC8yMy8yMDEzIDAyOjI5OjA1IFBN?=,
        =?UTF-8?B?Q1MgTm90aWNlIGNvbnZlcnRlZCB0byBpQ2FsZW5kYXIgZm9ybWF0W0xvY2Fs?=
 =?UTF-8?B?XSBieSBSb3V0ZXIgb24gTE5IUTA4TVRBKFJlbGVhc2UgOC41LjNGUDJ8?=
 =?UTF-8?B?SnVseSAwMiwgMjAxMikgYXQgMTAvMjMvMjAxMyAwMjoyOTowNyBQTQ==?=;
 type=501; name=$CSTrack

Any suggestions for fixing this or working around it?

Thanks in advance.

Don Badrak