[DRE-maint] Bug#733887: bsfilter: I got error "undefined method `force_encoding'" when learned as spam

[KISE Hiroshi]

Package: bsfilter
Version: 1:1.0.19-1
Severity: important

Dear Maintainer,

I typed "ls" (learn-spam) on Mew 6.5, I got following error:

Learned as spam: /usr/bin/bsfilter:1059: undefined method `force_encoding' for "[\260\241-\364\244]+":String (NoMethodError)

When "lm" (mark-spam), I got no error.

My .mew.el has copy of elisp from
/usr/share/doc/bsfilter/examples/mua/mew6.4/mew.el.

My system use "ruby" as Ruby 1.8.

$ ruby -v
ruby 1.8.7 (2012-02-08 patchlevel 358) [x86_64-linux]
$ LANG= update-alternatives --display ruby
ruby - manual mode
  link currently points to /usr/bin/ruby1.8
/usr/bin/ruby1.8 - priority 50
  slave erb: /usr/bin/erb1.8
  slave erb.1.gz: /usr/share/man/man1/erb1.8.1.gz
  slave irb: /usr/bin/irb1.8
  slave irb.1.gz: /usr/share/man/man1/irb1.8.1.gz
  slave rdoc: /usr/bin/rdoc1.8
  slave rdoc.1.gz: /usr/share/man/man1/rdoc1.8.1.gz
  slave ri: /usr/bin/ri1.8
  slave ri.1.gz: /usr/share/man/man1/ri1.8.1.gz
  slave ruby.1.gz: /usr/share/man/man1/ruby1.8.1.gz
  slave testrb: /usr/bin/testrb1.8
  slave testrb.1.gz: /usr/share/man/man1/testrb1.8.1.gz
/usr/bin/ruby1.9.1 - priority 51
  slave erb: /usr/bin/erb1.9.1
  slave erb.1.gz: /usr/share/man/man1/erb1.9.1.1.gz
  slave irb: /usr/bin/irb1.9.1
  slave irb.1.gz: /usr/share/man/man1/irb1.9.1.1.gz
  slave rdoc: /usr/bin/rdoc1.9.1
  slave rdoc.1.gz: /usr/share/man/man1/rdoc1.9.1.1.gz
  slave ri: /usr/bin/ri1.9.1
  slave ri.1.gz: /usr/share/man/man1/ri1.9.1.1.gz
  slave ruby.1.gz: /usr/share/man/man1/ruby1.9.1.1.gz
  slave testrb: /usr/bin/testrb1.9.1
  slave testrb.1.gz: /usr/share/man/man1/testrb1.9.1.1.gz
Current 'best' version is '/usr/bin/ruby1.9.1'.
$ 

Thank you.

-- System Information:
Debian Release: jessie/sid
  APT prefers testing
  APT policy: (1001, 'testing')
Architecture: amd64 (x86_64)

Kernel: Linux 3.11-2-amd64 (SMP w/2 CPU cores)
Locale: LANG=ja_JP.UTF-8, LC_CTYPE=ja_JP.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/bash

Versions of packages bsfilter depends on:
ii  ruby                          1:1.9.3
ii  ruby1.8 [ruby-interpreter]    1.8.7.358-9
ii  ruby1.9.1 [ruby-interpreter]  1.9.3.484-1

bsfilter recommends no packages.

Versions of packages bsfilter suggests:
ii  ruby-kakasi  2002.09.28-3
pn  ruby-qdbm    <none>

-- debconf-show failed