handbrake doesn't provide any feedback when it lacks permissions to read from device file

usually reading from `/dev/dvd` and other is no problem whereas a use case where one wants to read from e.g. `/dev/loopN` is imaginable. Even if the use case is not supposed to be covered a proper feedback if the permissions are missing should be provided.

ProblemType: Bug
DistroRelease: Ubuntu 15.04
Package: handbrake 0.9.9+svn6422+dfsg1-2
Uname: Linux 4.0.1-040001-generic x86_64
ApportVersion: 2.17.2-0ubuntu1.1
Architecture: amd64
CurrentDesktop: Unity
Date: Sun May 24 00:00:45 2015
EcryptfsInUse: Yes
InstallationDate: Installed on 2015-04-02 (51 days ago)
InstallationMedia: Ubuntu 15.04 "Vivid Vervet" - Beta amd64 (20150326)
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=de_DE.UTF-8
 SHELL=/bin/bash
SourcePackage: handbrake
SystemImageInfo:
 current build number: 0
 device name:
 channel: daily
 last update: Unknown
UpgradeStatus: No upgrade log present (probably fresh install)