musicxml2ly problems

[James E. Bailey]

Hello, I'm finding some old(er) files on my computer that I'd like to  
work with again, but this time in Lilypond. I'm converting them from  
Finale using musicxml. Unfortunately, the files don't convert and  
this is what I get:
James-TiGERmac:/Applications/LilyPond.app/Contents/Resources/bin/ 
musicxml2ly -r -v -l deutsch lasciatemi\ morire.xml
Reading MusicXML from lasciatemi morire.xml ...
Converting to LilyPond expressions...
Converting to LilyPond expressions...
Converting to LilyPond expressions...
Converting to LilyPond expressions...
Output to `lasciatemi morire-defs.ly'
Traceback (most recent call last):
  File "/Applications/LilyPond.app/Contents/Resources/bin/ 
musicxml2ly", line 1926, in ?
    main()
  File "/Applications/LilyPond.app/Contents/Resources/bin/ 
musicxml2ly", line 1921, in main
    voices = convert (filename, options)
  File "/Applications/LilyPond.app/Contents/Resources/bin/ 
musicxml2ly", line 1870, in convert
    print_ly_additional_definitions (printer, filename)
  File "/Applications/LilyPond.app/Contents/Resources/bin/ 
musicxml2ly", line 1789, in print_ly_additional_definitions
    for a in set(needed_additional_definitions):
NameError: global name 'set' is not defined

The output of the file is:

\version "2.11.37"
% automatically converted from lasciatemi morire.xml

%% additional definitions required by the score:

And I don't get the appropriate lasciatemi\ morire.ly file that I  
should get. I've been able to do this conversion in the past, but for  
some reason now it isn't working for me. Did I do something to offend  
Lilypond?