HTML archive generation failed if language set to Finnish

[Villes-users]

In version 2.1.5 of Mailman I discovered following
behaviour
while creating HTML-archive with bin/arch.

If list language is set to Finnish web archive creating
failed and
index.html size is 0.

But after I change language to English (or any other
language), everything works fine.

I tried same thing with other lists and different
emails and found
same behaviour.

(Language English)
/l/mailman/data/logs # ../../bin/arch just-somelist

#00000 <email address hidden>
figuring article archives
2004
Updating index files for archive [2004]
  Date
  Subject
  Author
  Thread
Computing threaded index
Updating HTML for article 1
Pickling archive state into
/l/mailman/data/archives/private/just-somelist/pipermail.pck

(Language Finnish)
/l/mailman/data/logs # ../../bin/arch just-somelist

#00000 <email address hidden>
tutkitaan artikkeliarkistoa
2004
Päivitetään indeksi-tiedostot arkistolle [2004]
  Date
  Subject
  Author
  Ketju
Luodaan viestipuuta
Päivitetään HTML-sivut artikkelille 1
Traceback (most recent call last):
  File "../../bin/arch", line 187, in ?
    main()
  File "../../bin/arch", line 177, in main
    archiver.close()
  File
"/l/mailman/latest/Mailman/Archiver/pipermail.py", line
313, in close
    self.write_TOC()
  File
"/l/mailman/latest/Mailman/Archiver/HyperArch.py", line
1051, in write_TOC
    toc.write(self.html_TOC())
  File
"/l/mailman/latest/Mailman/Archiver/HyperArch.py", line
740, in html_TOC
    accum.append(self.html_TOC_entry(a))
  File
"/l/mailman/latest/Mailman/Archiver/HyperArch.py", line
766, in html_TOC_entry
    templ = '<td><A href="%(url)s">[ ' +
_('Text%(sz)s') + ']</a></td>'
  File "/l/mailman/latest/Mailman/i18n.py", line 89, in _
    return tns % dict
ValueError: unsupported format character 'ä'
(0xffffffe4) at index 11
zsh: 24651 exit 1 ../../bin/arch just-somelist

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