The README in source tarball says ...
Additiionally, i would appreciate if libglade and pycairo are at least in a .sug file mentioned. You would get a similiar result with depfinder.Requirements
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* C compiler (GCC and MSVC supported)
* Python 2.3.5 or higher
* PyGObject 2.12.1 or higher
* Glib 2.8.0 or higher
* GTK+ 2.8.0 or higher (optional) or
GTK+ 2.10.0 or higher for 2.10 API
GTK+ 2.12.0 or higher for 2.12 API
GTK+ 2.14.0 or higher for 2.14 API
* libglade 2.5.0 or higher (optional)
* pycairo 1.0.2 or higher (optional)
* Numeric (optional)
Background: avahi requires definitely pygobject, libglade and pycairo installed. And there is some other problem that is really strange for me, pygtk does not work in Salix Core, there is no gdk module available, although pygobject, pycairo and libglade installed.