It's a debug message printed if XML module option `foldattributes` is specified i.e. with arguments `-o debug -o foldattributes`. When processing a non-inline tag. the rest is pretty much self-explanatory: In file foo.xml (first %s): "foldattributes" (setting name) setting is ignored because the tag '<bar>' (second %s) is not an inline tag". This can be helpful to debug why foldattributes is not kicking in when you want it to e.g. if you forgot to pass `-o inline='<bar>'`. For how "foldattributes" actually works and what inline tags are, see the module documentation: https://po4a.org/man/man3/Locale%3A%3APo4a%3A%3AXml.3pm.php