PDF doc build is broken on recent Fedora

By chance I tried to build our PDF docs on a Fedora 30
installation, and it doesn't work.  xsltproc seems to
get hung up in a tight loop before it starts to produce
any output.  The HTML build works fine, though.

Relevant package versions:

docbook-style-xsl-1.79.2-9.fc30.noarch
libxslt-1.1.33-1.fc30.x86_64

Anybody seen this, or have an idea what to poke at?

            regards, tom lane