make doc, problem with bibtex

[Federico Bruni]

'make doc' is returning the error below, can you help me?

make[2]: Entering directory '/home/fede/lilypond-git/Documentation'
BSTINPUTS=./essay /home/fede/lilypond-git/scripts/build/out/bib2texi \
-s /home/fede/lilypond-git/Documentation/lily-bib \
-o ./out-www/colorado.itexi \
-q \
./essay/colorado.bib

bibtex: Not writing to /home/fede/.cache/tmpzYBXQHbib2texi.blg 
(openout_any = p).
I couldn't open file name `/home/fede/.cache/tmpzYBXQHbib2texi.blg'
Bibtex exited with nonzero exit status!GNUmakefile:118: recipe for 
target 'out-www/colorado.itexi' failed
make[2]: *** [out-www/colorado.itexi] Error 1
make[2]: Leaving directory '/home/fede/lilypond-git/Documentation'
/home/fede/lilypond-git/stepmake/stepmake/generic-targets.make:166: 
recipe for target 'WWW-1' failed
make[1]: *** [WWW-1] Error 2
make[1]: Leaving directory '/home/fede/lilypond-git'
/home/fede/lilypond-git/stepmake/stepmake/generic-targets.make:182: 
recipe for target 'doc-stage-1' failed
make: *** [doc-stage-1] Error 2

address@hidden:~/lilypond-git$ ls ../.cache/tmpzYBXQHbib2texi
tmpzYBXQHbib2texi tmpzYBXQHbib2texi.aux

.blg file is not there.


$ apt-cache policy texlive-bibtex-extra | grep Installed
 Installed: 2014.20141024-1

Probably not related, but some days ago I changed default TMPDIR (/tmp) 
to save some space on / partition:

$ echo $TMPDIR
/home/fede/.cache