build fails

[Sergey Matveychuk]

I'v tried to build a fresh en_US.ISO8859-1/books/developers-handbook and 
got:
% make
/usr/local/bin/peps -p -r 100  -o 
/usr/src/doc/en_US.ISO8859-1/books/developers-handbook/../../../share/images/books/developers-handbook/sockets/layers.png 
`/bin/realpath 
/usr/src/doc/en_US.ISO8859-1/books/developers-handbook/../../../share/images/books/developers-handbook/sockets/layers.eps`
pnmtopng: bad magic number - not a ppm, pgm, or pbm file
*** Error code 1

Stop in /usr/src/doc/en_US.ISO8859-1/books/developers-handbook.

netpbm is fresh.
What is wrong?

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Sem.