[xml] catalog problem with xmlto

[Uwe Fechner <ufechner sk28 de>]

Hello,

I am using gentoo linux.

I have problems to use catalogs.
If I try to install (called "emerge" in gentoo linux) the package xmlto 
I get the error message:

warning: failed to load external entity 
"http://docbook.sourceforge.net/release/xsl/current/manpages/docbook.xsl";
compilation error: file 
/var/tmp/portage/xmlto-0.0.18/temp/xmlto-xsl.VYRlh4 line 4 element import
xsl:import : unable to load 
http://docbook.sourceforge.net/release/xsl/current/manpages/docbook.xsl
warning: failed to load external entity 
"http://docbook.sourceforge.net/release/xsl/current/manpages/docbook.xsl";
compilation error: file 
/var/tmp/portage/xmlto-0.0.18/temp/xmlto-xsl.TRDJdu line 4 element import
xsl:import : unable to load 
http://docbook.sourceforge.net/release/xsl/current/manpages/docbook.xsl

Q: I'm trying to build xmlto on my Debian box, but it doesn't work.

A: If you get `Attempt to load network entity' errors when building
  xmlto, your system does not have the required support for XML
  Catalogs
  (http://www.oasis-open.org/committees/entity/spec-2001-08-06.html).
  In particular, Debian has no support for these.  Try the Fedora
  Project <http://fedora.redhat.com>.
make[1]: *** [man/man1/xmlto.1] Error 1
make[1]: Leaving directory `/var/tmp/portage/xmlto-0.0.18/work/xmlto-0.0.18'
make: *** [all] Error 2

I don't use debian, I have the file docbook.xsl installed locally, the url:
http://docbook.sourceforge.net/release/xsl/current/manpages/docbook.xsl
can be resolved via internet (using wget), still I get this error message.

The gentoo package maintainer doesn't understand the reason of this problem.

How can I debug, if xml catalogs for xsl transformations work correctly 
on my
system?

(I am using libxml2 2.6.19)

Any help appreciated.

Uwe Fechner