Version is actually 2.13, from debian testing, but that is not an option
Several programs (in particular, thunar and fc-cache) that use the library generated errors:
"Fontconfig error: failed reading config file"
This was repeated five times. It turned out that some font install had put five subdirectories under /etc/fonts/conf.available. That install had put its .conf files in those subdirectories (as well as a misnamed .conf file in /etc/fonts/conf.available). The primary failure was in that other install, of course, but it would have been helpful if the error message from Fontconfig had included more information. At the very least including the name of the .conf file (including the full path if possible) would have helped give me a head start in solving the problem.
thanks. fixed in git cfb21c7