/usr/doc can not be build neither can it be installed

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Hello FreeBSD users out there.

My last build and update of /usr/doc was end of May 2017; since then any attempt building
the doc from /usr/doc failed on 12-CURRENT to 12-STABLE and now on 13-CURRENT.

I believe all the required ports (following the instructions from fdp-primer and other
instructions given by the official web sites providing newest docs) are up to date and
the /usr/doc tree is also at its most recent revision (using svn):

# svn info
Path: .
Working Copy Root Path: /usr/doc
URL: https://svn.freebsd.org/doc/head

Relative URL: ^/head
Repository Root: https://svn.freebsd.org/doc

Repository UUID: c2e8774f-c49f-e111-b436-862b2bbc8956
Revision: 52697
Node Kind: directory
Schedule: normal
Last Changed Author: ryusuke
Last Changed Rev: 52697
Last Changed Date: 2018-12-18 12:49:16 +0100 (Tue, 18 Dec 2018)

Apart from any other language (i.e. German) I'd expect that the en_US version would build
at least, but whenever I issue:

cd /usr/doc
make clean
make update
make all

the build ends up in 

[...]

egrep: chapters.ent: No such file or directory
env
XML_CATALOG_FILES="file:///usr/obj/usr/doc/en_US.ISO8859-1/books/handbook/catalog-cwd.xml
file:///usr/doc/en_US.ISO8859-1/share/xml/catalog.xml
file:///usr/doc/share/xml/catalog.xml
file:///usr/local/share/xml/catalog" /usr/local/bin/xmllint --nonet --noent --valid
- --dropdtd --xinclude /usr/doc/en_US.ISO8859-1/books/handbook/book.xml >
book.parsed.xml.tmp warning: failed to load external entity
"/usr/doc/en_US.ISO8859-1/books/handbook/mirrors.xml.ftp.index.inc" /usr/doc/en_US.ISO8859-1/books/handbook/mirrors/chapter.xml:100:
parser error : Failure to process entity chap.mirrors.ftp.index.inc
&chap.mirrors.ftp.index.inc;
^ /usr/doc/en_US.ISO8859-1/books/handbook/mirrors/chapter.xml:100: parser error : Entity
'chap.mirrors.ftp.index.inc' not defined &chap.mirrors.ftp.index.inc; ^ warning: failed
to load external entity
"/usr/doc/en_US.ISO8859-1/books/handbook/mirrors.lastmod.inc" /usr/doc/en_US.ISO8859-1/books/handbook/mirrors/chapter.xml:102:
parser error : Failure to process entity chap.mirrors.lastmod.inc
&chap.mirrors.lastmod.inc;
^ /usr/doc/en_US.ISO8859-1/books/handbook/mirrors/chapter.xml:102: parser error : Entity
'chap.mirrors.lastmod.inc' not defined &chap.mirrors.lastmod.inc;

[...]

My first countermeasure was to recompile/reinstall every port possibly involved, but that
did not resolve the problem.

A similar situation is with poudriere builds and traditional builds of ports
misc/freebsd-doc-en and misc/freebsd-doc-de. They end up in a similar failure on all
systems I've running FBSD 13-CURRENT and 12-STABLE so far.

Can someone please look into this and fix the problem or point me to my mistake? I'm out
of clues.

Thanks in advance and kind regards,

O. Hartmann

- -- 
O. Hartmann

Ich widerspreche der Nutzung oder Übermittlung meiner Daten für
Werbezwecke oder für die Markt- oder Meinungsforschung (§ 28 Abs. 4 BDSG).
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