config_list breaks at filter_mime_types

When running:

config_list -o cpunk.conf cpunk-secpro

on my list cpunk-secpro@lists.thecabal.org, I get the
following error:

(bofh:mailman) /home/mailman $ config_list -o
cpunk.conf cpunk-secpro
Traceback (most recent call last):
File "/home/mailman/bin/config_list", line 268, in ?
main()
File "/home/mailman/bin/config_list", line 261, in main
do_output(listname, outfile)
File "/home/mailman/bin/config_list", line 113, in
do_output
do_list_categories(mlist, k, None, outfp)
File "/home/mailman/bin/config_list", line 162, in
do_list_categories
lines = value.replace('\r', '').split('\n')
AttributeError: 'list' object has no attribute 'replace'

Doing a tail of the cpunk.conf file show the following:

(bofh:mailman) /home/mailman $ tail
cpunk.conf
# matching MIME major type, e.g. image. Blank lines
are ignored.
#
# After stripping message parts, any multipart
attachment that is empty
# as a result is removed all together. If the outer part's
MIME type
# matches one of the strip types, or if all of the outer
part's subparts
# are stripped, then the whole message is discarded.
Finally, each
# multipart/alternative section will be replaced by just
the first
# alternative that is non-empty after the specified types
have been
# removed.
filter_mime_types =