phablet@ubuntu-phablet:~$ libertine-launch bar /usr/bin/vlc
Traceback (most recent call last):
  File "/usr/bin/libertine-launch", line 59, in <module>
    session_bridge = launch_libertine_session_bridge()
  File "/usr/bin/libertine-launch", line 42, in launch_libertine_session_bridge
    libertine_session_bridge_cmd = "libertine-session-bridge " + set_dbus_session_socket_path()
  File "/usr/bin/libertine-launch", line 28, in set_dbus_session_socket_path
    unique_id = os.environ['DISPLAY'].strip(':')
  File "/usr/lib/python3.4/os.py", line 633, in __getitem__
    raise KeyError(key) from None
KeyError: 'DISPLAY'
phablet@ubuntu-phablet:~$