Comment 2 for bug 1044245

This is happening because an entry is missing from diagnostics_en.xml, at least that is my understanding. It is happening a lot with JSONiq features.

The assertion is probably useful, but it doesn't give enough information. We need it to explicitly say "I am crapping out because you used the key "~FooBarBaz" in an error but there is no localized value for that key in diagnostics_en.xml", possibly even with a pointer to the correct file to update and where the missing data should be placed.