/usr/lib/python2.7/dist-packages/gtk-2.0/gtk/__init__.py:57: GtkWarning: could not open display
  warnings.warn(str(e), _gtk.Warning)
/home/pi/py_test/Gstreamer-webcam-tool-master/ssGUI.py:56: Warning: invalid (NULL) pointer instance
  self.window = gtk.Window(gtk.WINDOW_TOPLEVEL)
/home/pi/py_test/Gstreamer-webcam-tool-master/ssGUI.py:56: Warning: g_signal_connect_data: assertion 'G_TYPE_CHECK_INSTANCE (instance)' failed
  self.window = gtk.Window(gtk.WINDOW_TOPLEVEL)
/home/pi/py_test/Gstreamer-webcam-tool-master/ssGUI.py:76: Warning: Attempt to add property GtkSettings::gtk-label-select-on-focus after class was initialised
  hbox.pack_start(gtk.Label())
/home/pi/py_test/Gstreamer-webcam-tool-master/ssGUI.py:77: Warning: Attempt to add property GtkSettings::gtk-button-images after class was initialised
  self.button = gtk.Button("Snap")
/home/pi/py_test/Gstreamer-webcam-tool-master/ssGUI.py:77: GtkWarning: IA__gtk_settings_get_for_screen: assertion 'GDK_IS_SCREEN (screen)' failed
  self.button = gtk.Button("Snap")
/home/pi/py_test/Gstreamer-webcam-tool-master/ssGUI.py:77: Warning: g_object_get: assertion 'G_IS_OBJECT (object)' failed
  self.button = gtk.Button("Snap")
gstreamer video pipeline : v4l2src device=/dev/video0 ! video/x-raw-yuv,width=640,height=480,framerate=30/1 ! xvimagesink
Traceback (most recent call last):
  File "demo.py", line 22, in <module>
    cam = WebcamManager(device, resolution, snap_format)
  File "/home/pi/py_test/Gstreamer-webcam-tool-master/ssGUI.py", line 50, in __init__
    self.create_video_pipeline()
  File "/home/pi/py_test/Gstreamer-webcam-tool-master/ssGUI.py", line 89, in create_video_pipeline
    self.video_player = gst.parse_launch(video_pipeline) # create pipeline
glib.GError: no element "v4l2src"