Fixing small bug introduced by the Promise refactoring of lib/require.js, fs.exists cannot be promisified since its callbacks do not include a possible error object.
Fixing small bug introduced by the Promise refactoring of lib/require.js, fs.exists cannot be promisified since its callbacks do not include a possible error object.

oneorangecat/kalabox,ari-gold/kalabox,rabellamy/kalabox,oneorangecat/kalabox,kalabox/kalabox-cli,ari-gold/kalabox,kalabox/kalabox-cli,ManatiCR/kalabox,RobLoach/kalabox,rabellamy/kalabox,ManatiCR/kalabox,RobLoach/kalabox