If I try to load a non-existent Qt resource, e.g.:

QFile f{":/does/not/exist"};
f.open(QFile::ReadOnly);

...it fails, as expected. However, QFile::errorString is set to a not very informative "Unknown error". It would be better if this gave something like "Resource not found" (bonus points for 'resource', but "File not found" would still be an improvement).