Improve exception message.
Improve exception message.

Refs #13390

cakephp/cakephp,CakeDC/cakephp,ADmad/cakephp,CakeDC/cakephp,ADmad/cakephp,ndm2/cakephp,dakota/cakephp,cakephp/cakephp,CakeDC/cakephp,CakeDC/cakephp,ADmad/cakephp,ndm2/cakephp,dakota/cakephp,ndm2/cakephp,ADmad/cakephp,ndm2/cakephp,cakephp/cakephp,dakota/cakephp,cakephp/cakephp,dakota/cakephp