Use the realpath to require the error files as HHVM does not resolve them in phars
Use the realpath to require the error files as HHVM does not resolve them in phars

This avoids loading the file twice on HHVM because it considers the 2 paths to be different even though they reference the same file when normalized.
Refs #1684
ezzatron/phpunit,SunDrop/phpunit,DonaldKellett/phpunit,bradgrohs/phpunit,dshafik/phpunit,Firehed/phpunit,zhaoyan158567/phpunit,FireWalkerX/phpunit,9040044/phpunit,kyale/phpunit,s001dxp/phpunit,didiwuliu/phpunit,abachi/phpunit,imshibaji/phpunit,m157y/phpunit,nonconforme/phpunit,Ma27/phpunit,eelf/phpunit,duncan3dc/phpunit,WebSeed/phpunit,nelson6e65/phpunit,ya7lelkom/phpunit,darol100/phpunit,sebastianbergmann/phpunit,malkusch/phpunit,beealone/phpunit,abacaphiliac/phpunit,masarakki/phpunit,stof/phpunit,Lance0312/phpunit,MajorCaiger/phpunit,Maks3w/phpunit,MartinhoOmura/phpunit,matheusgomes17/phpunit,CarsonF/phpunit,simohammedhttp/phpunit,serbanghita/phpunit,HappyRay/phpunit,lcp0578/phpunit,luomor/phpunit,tronsha/phpunit,asgrim/phpunit,chrisbjr/phpunit,Shaked/phpunit,OndraM/phpunit,giorgiosironi/phpunit