building manpages from docbook (or the docbook sgml toolchain)
Some packages (for now I'm aware of colord, will update as I find more) use docbook2man to generate manpages. There are two versions: one provided by docbook-utils and one by docbook2x.
docbook-utils fails to build and docbook2x builds but chokes on the doctype declaration of colord manpages (more details in the discussion of !12 (closed)).
I have a small patch to disable building the manpages if docbook2man isn't found, but we'll need a long term solution (which may involve updating the manpages to docbook 5.0).