lilypond-book error during test-baseline

[Dan Eble]

I hit an error building test-baseline after updating master.  This is what I 
did.

    rm -rf *
    ~/lilypond-src/autogen.sh —ci
    make -j7 CPU_COUNT=7 && time make -j7 CPU_COUNT=7 test-baseline

I couldn't reproduce it after making test-clean and test-baseline again.
The tail of the terminal output is below.
— 
Dan

Making input/regression/lilypond-book/out-test/texinfo-musicxml-file.texi < tely
Making input/regression/lilypond-book/out-test/texinfo-papersize-docs.texi < 
tely
Making input/regression/lilypond-book/out-test/suffix-latex.pdf < tex
Making input/regression/lilypond-book/out-test/suffix-lytex.pdf < tex
Making input/regression/lilypond-book/out-test/suffix-lyxml.pdf < xml
Traceback (most recent call last):
  File "/home/user/lilypond-src/scripts/lilypond-book.py", line 733, in <module>
    main()
  File "/home/user/lilypond-src/scripts/lilypond-book.py", line 717, in main
    write_output_documents(chunks, is_filter=False)
  File "/home/user/lilypond-src/scripts/lilypond-book.py", line 636, in 
write_output_documents
    s = ch.replacement_text()
  File "/home/user/lilypond-src/python/book_snippets.py", line 844, in 
replacement_text
    return self.formatter.snippet_output(base, self)
  File "/home/user/lilypond-src/python/book_texinfo.py", line 382, in 
snippet_output
    doctitle = open(fullpath, 'r', encoding='utf-8').read()
FileNotFoundError: [Errno 2] No such file or directory: 
'/home/user/lilypond-build/input/regression/lilypond-book/out-test/c9/lily-08ef596f.doctitlees'
Making input/regression/lilypond-book/out-test/suffix-tely.html < texi
make[3]: *** 
[/home/user/lilypond-src/./input/regression/lilypond-book/GNUmakefile:89: 
out-test/texinfo-include-language-detection.texi] Error 1
make[3]: *** Waiting for unfinished jobs....
make[2]: *** 
[/home/user/lilypond-src/./input/regression/lilypond-book/GNUmakefile:19: 
local-test] Error 2
make[1]: *** [/home/user/lilypond-src/GNUmakefile.in:317: test] Error 2
make: *** [/home/user/lilypond-src/GNUmakefile.in:325: test-baseline-pre] Error 
2

real    2m58.579s
user    5m29.593s
sys     0m43.431s