Handled permissions error in file storage adapter
Handled permissions error in file storage adapter

no issue

- trying to read a file without the correct permissions would cause a
  500 error
- this commit handles the error code and returns an appropriate
  response

kevinansfield/Ghost,ErisDS/Ghost,JohnONolan/Ghost,TryGhost/Ghost,janvt/Ghost,kevinansfield/Ghost,e10/Ghost,bitjson/Ghost,ErisDS/Ghost,bitjson/Ghost,TryGhost/Ghost,e10/Ghost,kevinansfield/Ghost,JohnONolan/Ghost,TryGhost/Ghost,ErisDS/Ghost,JohnONolan/Ghost,janvt/Ghost