This error is due to a missing dependency in debian/control. Adding asciidoc to Build-Depends-Indep should fix it.
-Build-Depends-Indep: docbook-xml, docbook-xsl, xsltproc +Build-Depends-Indep: docbook-xml, docbook-xsl, xsltproc, asciidoc -- Andres E. Rodriguez Lazo (RoAkSoAx) Ingeniero de Sistemas Official Ubuntu Member Ubuntu Counter Project - User # 17582
