Update doc block to indicate absolute path requirement.
Update doc block to indicate absolute path requirement.

Fixes #12567

mvdriel/cakephp,cakephp/cakephp,dakota/cakephp,ADmad/cakephp,CakeDC/cakephp,ndm2/cakephp,CakeDC/cakephp,davidyell/cakephp,davidyell/cakephp,ndm2/cakephp,ADmad/cakephp,dakota/cakephp,mvdriel/cakephp,tenkoma/cakephp,tenkoma/cakephp,garethellis36/cakephp,garethellis36/cakephp,garethellis36/cakephp,petteyg/cakephp,petteyg/cakephp,cakephp/cakephp,cakephp/cakephp,CakeDC/cakephp,ndm2/cakephp,davidyell/cakephp,ADmad/cakephp,cakephp/cakephp,tenkoma/cakephp,mvdriel/cakephp,dakota/cakephp,ADmad/cakephp,petteyg/cakephp,petteyg/cakephp,tenkoma/cakephp,garethellis36/cakephp,mvdriel/cakephp,ndm2/cakephp,dakota/cakephp,CakeDC/cakephp