[Mailman-Users] Accect [%xxx] in the Header added to mail

[Andrea]

Hello,
I need to add a '%xxx' string to the header of each message sent using
Mailman.

I get an error message because '%xxx' is recognized as a Mailman
variable and the software tries to replace it with something it can't
find:
<<
  File "/usr/local/mailman/Mailman/Handlers/Decorate.py", line 39, in
process
    header = string.replace(mlist.msg_header % d, '\r\n', '\n')
AttributeError: SafeDict instance has no attribute '__int__'
>>

Is it possible to make Mailman not to replace this string in the
header? I tried to change Decorate.py file but I'm not a python
programmer and it didn't work.

Thanks in advance for your help.

Regards
Andrea Fava

P.S. Version is use: 2.0.13