Starting OpenLP on Linux without VLC causes traceback

[Tomas Groth]

Found in 2.1.6 on Linux.

Starting OpenLP on Linux without VLC installed causes a traceback and OpenLP doesn't start.

The traceback:

$ ./openlp.py -ld
Traceback (most recent call last):
  File "/home/tgc/projects/OpenLP/code/trunk/openlp/core/ui/media/vendor/vlc.py", line 106, in find_lib
    dll = ctypes.CDLL(p)
  File "/usr/lib/python3.4/ctypes/__init__.py", line 351, in __init__
    self._handle = _dlopen(self._name, mode)
OSError: libvlc.so.5: cannot open shared object file: No such file or directory

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "./openlp.py", line 27, in <module>
    from openlp.core.common import is_win, is_macosx
  File "/home/tgc/projects/OpenLP/code/trunk/openlp/__init__.py", line 26, in <module>
    from openlp import core, plugins
  File "/home/tgc/projects/OpenLP/code/trunk/openlp/core/__init__.py", line 46, in <module>
    from openlp.core.ui.exceptionform import ExceptionForm
  File "/home/tgc/projects/OpenLP/code/trunk/openlp/core/ui/exceptionform.py", line 76, in <module>
    from openlp.core.ui.media.vlcplayer import VERSION
  File "/home/tgc/projects/OpenLP/code/trunk/openlp/core/ui/media/vlcplayer.py", line 106, in <module>
    if get_vlc() and is_linux() and 'nose' not in sys.argv[0]:
  File "/home/tgc/projects/OpenLP/code/trunk/openlp/core/ui/media/vlcplayer.py", line 74, in get_vlc
    from openlp.core.ui.media.vendor import vlc
  File "/home/tgc/projects/OpenLP/code/trunk/openlp/core/ui/media/vendor/vlc.py", line 167, in <module>
    dll, plugin_path = find_lib()
  File "/home/tgc/projects/OpenLP/code/trunk/openlp/core/ui/media/vendor/vlc.py", line 108, in find_lib
    dll = ctypes.CDLL('libvlc.so.5')
  File "/usr/lib/python3.4/ctypes/__init__.py", line 351, in __init__
    self._handle = _dlopen(self._name, mode)
OSError: libvlc.so.5: cannot open shared object file: No such file or directory