Devhelp index file format warning
(devhelp:8932): devhelp-WARNING **: 13:39:23.282:
The file 'file:///usr/share/gtk-doc/html/libxml2/libxml2.devhelp'
uses the Devhelp index file format version 1, which is deprecated.
A future version of Devhelp may remove the support for the format version 1.
The index file should be ported to the Devhelp index file format version 2.