TINY-2978: updated assert error messages
TINY-2978: updated assert error messages

tinymce/tinymce,TeamupCom/tinymce,FernCreek/tinymce,FernCreek/tinymce,tinymce/tinymce,danielpunkass/tinymce,TeamupCom/tinymce,danielpunkass/tinymce,tinymce/tinymce,danielpunkass/tinymce,FernCreek/tinymce