fix: [ 926034 ] Crashes on encoding errors

Actually the bug title is wrong, the problem is (I
think) python not supporting windows-1250 and windows-1252.
The problem can be fixed in the email library in
$MAILMANDIR/pythonlib/email/Header.py
I don't know if newer pythons (afaik python 2.3
contains this email package and maybe it does handle
windows codepages) still suffer the same problem.
So here's my solution for mailman-2.1.3 (I think it's
applicable to 2.1.4 too) and python 2.2.2:

--- Header.py.orig 2003-03-30 22:39:05.000000000 +0200
+++ Header.py 2004-05-18 12:01:35.000000000 +0200
@@ -284,7 +284,7 @@
                         outcodec =
charset.output_codec or 'us-ascii'
                         s = s.encode(outcodec, errors)
                         break
- except UnicodeError:
+ except (UnicodeError, LookupError):
                         pass
                 else:
                     assert False, 'utf-8 conversion
failed'

this way if s.encode does not understand the original
encoding (like windows-1250 or windows-1252) then it
resorts to use utf-8