failing invocation of hts provides no feedback

[Karl-Philipp Richter]

Entering `hts --forward-port localhost:1237 --no-daemon example.com:443` provides no feedback and fails with returncode 1. That's unhelpful.

This seems to be caused by missing root permissions, however all failure cases should be covered and provide useful output.

ProblemType: Bug
DistroRelease: Ubuntu 15.04
Package: httptunnel 3.3+dfsg-3
Uname: Linux 4.0.3-040003-generic x86_64
ApportVersion: 2.17.2-0ubuntu1
Architecture: amd64
Date: Sat May 16 09:28:25 2015
Dependencies:
 gcc-5-base 5.1~rc1-0ubuntu1
 libc6 2.21-0ubuntu4
 libgcc1 1:5.1~rc1-0ubuntu1
 multiarch-support 2.21-0ubuntu4
EcryptfsInUse: Yes
InstallationDate: Installed on 2015-04-20 (25 days ago)
InstallationMedia: Ubuntu-Server 14.10 "Utopic Unicorn" - Release amd64 (20141022.2)
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=de_DE.UTF-8
 SHELL=/bin/bash
SourcePackage: httptunnel
UpgradeStatus: Upgraded to vivid on 2015-04-24 (21 days ago)