Minor change

src/nxhdf5.cpp

@@ -1562,7 +1562,8 @@ private:
             CloseDataSet();
             H5::CommonFG* fg = GetTopOrFile<H5::CommonFG>();
             if (!fg)
-                throw NexusException("can't open a group without a parent group or file", "NexusFileImpl::PrivOpenGroup");
+                throw NexusException(yat::SFormat("can't open group ({}({}) in {}) without a parent group or file")
+                                    % groupName % className % file_path_, "NexusFileImpl::PrivOpenGroup");
             /// open the group
             H5::Group group = fg->openGroup(groupName);
             /// check group class