musicxml2ly: AttributeError: PartGroupInfo instance has no attribute 'set_part_information'

[Dag Odenhall]

Hello list,

I get this traceback trying to convert the Reunion demo score from
MuseScore:

musicxml2ly: Reading MusicXML from Reunion.xml ...
musicxml2ly: Converting to LilyPond expressions...
musicxml2ly: Converting to LilyPond expressions...
musicxml2ly: Converting to LilyPond expressions...
musicxml2ly: Converting to LilyPond expressions...
musicxml2ly: Converting to LilyPond expressions...
musicxml2ly: Converting to LilyPond expressions...
Traceback (most recent call last):
  File "/usr/bin/musicxml2ly", line 2986, in <module>
    main()
  File "/usr/bin/musicxml2ly", line 2981, in main
    voices = convert (filename, options)
  File "/usr/bin/musicxml2ly", line 2896, in convert
    update_score_setup (score, part_list, voices)
  File "/usr/bin/musicxml2ly", line 2794, in update_score_setup
    score_structure.set_part_information (part_id, staves_info)
  File "/usr/share/lilypond/2.19.43/python/musicexp.py", line 1941, in
set_part_information
    self.contents.set_part_information (part_id, staves_info)
  File "/usr/share/lilypond/2.19.43/python/musicexp.py", line 1780, in
set_part_information
    c.set_part_information (part_name, staves_info)
AttributeError: PartGroupInfo instance has no attribute
'set_part_information'

The MusicXML file is available here:
https://musescore.com/marcsabatella/reunion

I haven't been able to reproduce this myself with a smaller score, but
Reunion works if I remove these lines:

    <part-group type="start" number="1">
      <group-symbol>brace</group-symbol>
      </part-group>

That bit seems to be redundant anyway in this case according to the
MusicXML specification, although it doesn't seem to be wrong either.

If I add a stub set_staff_information method to PartGroupInfo it also works
but I get this warning instead:

musicxml2ly: warning: Unprocessed PartGroupInfo <__main__.PartGroupInfo
instance at ...> encountered

Maybe this is a bug in the score, or in MuseScore's MusicXML exporter? Even
so, musicxml2ly could perhaps handle faulty scores more gracefully than a
traceback or obscure warning. It doesn't look like a bug in the XML to me,
though. I ran it against the schema and it only complained about something
unrelated:

The 'dynamics' attribute is invalid - The value '-1.11' is invalid
according to its datatype 'non-negative-decimal' - The MinInclusive
constraint failed.

(which in deed seems to be an error and probably a bug in MuseScore.)

Cheers,
Dag