OK, I think I know what's going on.
The bug triggers when all the following conditions are met:
* /usr/local/share exists prior to installation of the
"fontconfig-config" package. (It's supposed to be created by base-files,
but it didn't exist in my chroot for some reason...)
* The building user belongs to the "staff" group.
* No other program created the UUID file for /usr/local/share/fonts
yet.
This is what happens:
1. fontconfig-config.postist creates /usr/local/share/fonts/, owned by
root:staff, mode 2775. (This is violation of Policy ยง9.1.2: unless
/etc/staff-group-for-usr-local exists, directories in /usr/local should
be root:root 0755.)
2. pdf2djvu (indirectly) calls the FcDirCacheCreateUUID() function...
2.1. FcDirCacheCreateUUID creates an UUID file in
/usr/local/share/fonts/. This succeeds, because the user has write
access to the directory.
2.2. FcDirCacheCreateUUID tries to change mtime of
/usr/local/share/fonts/. But, as documented in the utimes(2) manpage,
write access is not enough to do that: you need to be either the file
owner, or root (or have root-like capabilities). So this fails, and a
warning is issued.
Easy work-around for pdf2djvu: add the "fontconfig" package to
Build-Depends. It will take care take of creating the UUID file for
/usr/local/share/fonts/, and then FcDirCacheCreateUUID() will be mostly
no-op.
--
Jakub Wilk
