Since there are fancy "in view" messages which show all loading trouble,
is there no need to fetch and show some error message.
See also https://phabricator.kde.org/D18117
I have it only poor tested with our big S&R file, so no test was made with other trouble causing stuff.
This need a patch in Kate, will try to link that
Is there a way to check wat is going on, 1) or 2) ? Guess, yes, and you can point me
Just for info: If openingErrorMessage is indeed not set anymore, this is a behavior change, since KTextEditor::Document::openingErrorMessage() is public API. Looking at lxr.kde.org, it seems this is not used (but ->openingError() is used, see https://lxr.kde.org/source/kde/applications/kate/addons/filetree/katefiletreemodel.cpp#0554).