Thought you guys wanted to see this, as you're the one maintaining docbook-utils:
https://bugs.launchpad.net/ubuntu/+source/docbook-utils/+bug/46716

The error in line 273 occurs if you have a your .docbook file is in a path that contains a space somewhere in the path and you run docbook2html from the .docbook source directory.
example:
/home/my test/docbook/ is the current directory and you have a test.docbook file in that folder.
Then while you're still in that folder, run docbook2html test.docbook

This generates the error in line 273.

Regards,
Espen Carlsen.