convert-ly error

[Nick Payne]

I've seen this error several times when running convert-ly. I think it must
be a timing problem of some sort because when I run the identical command
again it always succeeds on the 2nd execution:

Running 2.11.63 on XP.

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convert-ly.py --edit "C:\nick\Lilypond\Adagio\notes.ly"
convert-ly.py (GNU LilyPond) 2.11.63
Processing `C:\nick\Lilypond\Adagio\notes.ly'... 
Applying conversion: 2.11.2, 2.11.5, 2.11.6, 2.11.10, 2.11.11, 2.11.13,
2.11.15, 2.11.23, 2.11.35, 2.11.38, 2.11.46, 2.11.48, 2.11.50, 2.11.51,
2.11.52, 2.11.53, 2.11.55, 2.11.57, 2.11.60, 2.11.61, 2.11.62 Traceback
(most recent call last):
  File "c:\Program Files\LilyPond\usr\bin\convert-ly.py", line 318, in ?
    main ()
  File "c:\Program Files\LilyPond\usr\bin\convert-ly.py", line 312, in main
    do_one_file (f)
  File "c:\Program Files\LilyPond\usr\bin\convert-ly.py", line 263, in
do_one_file
    os.rename (infile_name, infile_name + '~')
OSError: [Errno 13] Permission denied
Processing time: 0 seconds

convert-ly.py --edit "C:\nick\Lilypond\Adagio\notes.ly"
convert-ly.py (GNU LilyPond) 2.11.63
Processing `C:\nick\Lilypond\Adagio\notes.ly'... 
Applying conversion: 2.11.2, 2.11.5, 2.11.6, 2.11.10, 2.11.11, 2.11.13,
2.11.15, 2.11.23, 2.11.35, 2.11.38, 2.11.46, 2.11.48, 2.11.50, 2.11.51,
2.11.52, 2.11.53, 2.11.55, 2.11.57, 2.11.60, 2.11.61, 2.11.62 Processing
time: 0 seconds

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Nick