Update error message when displayErrorDetails is false
Update error message when displayErrorDetails is false

Match more closely the Slim 2 error message.

dopesong/Slim,slimphp/Slim,designermonkey/Slim,RealSelf/Slim,foxyantho/Slim,iinux/Slim,iinux/Slim,iinux/Slim,JoeBengalen/Slim,feryardiant/slim,Sam-Burns/Slim,AndrewCarterUK/Slim,mnapoli/Slim,juliangut/Slim,akrabat/Slim