[Gimp-docs] 'make validate' no longer shows errors

[julien]

Hi,

I intentionnally created an error (2 <secondary> tags in a <indexterm>) 
in a sandbox without any error:
'make lint' is OK,
'make validate' gives Error 4, and does not tell where this error is.

I deleted the 2nd <secondary>: make validate : 0 error

There is something wrong in the validating process.

Greetings.

Julien