old_contents: #!/usr/bin/python3
  import sys, gi, signal
  
  gi.require_version('Gst', '1.0')
  from gi.repository import Gst, GstNet, GObject
  
  # init GObject & Co. before importing local classes
  GObject.threads_init()
  Gst.init([])
  
  class Source(object):
  	def __init__(self):
  		# it works much better with a local file
  		pipeline = """
  			videotestsrc pattern=ball foreground-color=0x00ff0000 background-color=0x00440000 !\
  				timeoverlay !
  				video/x-raw,format=I420,width=192,height=108,framerate=25/1,pixel-aspect-ratio=1/1 !\
  				mux. \
  			\
  			audiotestsrc freq=330 !\
  				audio/x-raw,format=S16LE,channels=2,layout=interleaved,rate=48000 !\
  				mux. \
  			\
  			matroskamux name=mux !\
  				tcpclientsink host=127.0.0.1 port=10000
  		"""
  
  		clock = Gst.SystemClock.obtain()
  		self.clock = GstNet.NetClientClock.new('voctocore', '127.0.0.1', 9998, clock.get_time())
  		print('obtained NetClientClock from host', self.clock)
  
  		self.senderPipeline = Gst.parse_launch(pipeline)
  		self.senderPipeline.use_clock(self.clock)
  		self.src = self.senderPipeline.get_by_name('src')
  
  		# Binding End-of-Stream-Signal on Source-Pipeline
  		self.senderPipeline.bus.add_signal_watch()
  		self.senderPipeline.bus.connect("message::eos", self.on_eos)
  		self.senderPipeline.bus.connect("message::error", self.on_error)
  
  		print("playing")
  		self.senderPipeline.set_state(Gst.State.PLAYING)
  
  
  	def on_eos(self, bus, message):
  		print('Received EOS-Signal')
  		sys.exit(1)
  
  	def on_error(self, bus, message):
  		print('Received Error-Signal')
  		(error, debug) = message.parse_error()
  		print('Error-Details: #%u: %s' % (error.code, debug))
  		sys.exit(1)
  
  def main():
  	signal.signal(signal.SIGINT, signal.SIG_DFL)
  
  	src = Source()
  
  	mainloop = GObject.MainLoop()
  	try:
  		mainloop.run()
  	except KeyboardInterrupt:
  		print('Terminated via Ctrl-C')
  
  
  if __name__ == '__main__':
  	main()
  
new_contents: #!/usr/bin/python3
  import sys, gi, signal
  
  gi.require_version('Gst', '1.0')
  from gi.repository import Gst, GstNet, GObject
  
  # init GObject & Co. before importing local classes
  GObject.threads_init()
  Gst.init([])
  
  class Source(object):
  	def __init__(self):
  		# it works much better with a local file
  		pipeline = """
  			videotestsrc pattern=ball foreground-color=0x00ff0000 background-color=0x00440000 !
  				timeoverlay !
  				video/x-raw,format=I420,width=192,height=108,framerate=25/1,pixel-aspect-ratio=1/1 !
  				mux.
  
  			audiotestsrc freq=330 !
  				audio/x-raw,format=S16LE,channels=2,layout=interleaved,rate=48000 !
  				mux.
  
  			matroskamux name=mux !
  				tcpclientsink host=127.0.0.1 port=10000
  		"""
  
  		clock = Gst.SystemClock.obtain()
  		self.clock = GstNet.NetClientClock.new('voctocore', '127.0.0.1', 9998, clock.get_time())
  		print('obtained NetClientClock from host', self.clock)
  
  		self.senderPipeline = Gst.parse_launch(pipeline)
  		self.senderPipeline.use_clock(self.clock)
  		self.src = self.senderPipeline.get_by_name('src')
  
  		# Binding End-of-Stream-Signal on Source-Pipeline
  		self.senderPipeline.bus.add_signal_watch()
  		self.senderPipeline.bus.connect("message::eos", self.on_eos)
  		self.senderPipeline.bus.connect("message::error", self.on_error)
  
  		print("playing")
  		self.senderPipeline.set_state(Gst.State.PLAYING)
  
  
  	def on_eos(self, bus, message):
  		print('Received EOS-Signal')
  		sys.exit(1)
  
  	def on_error(self, bus, message):
  		print('Received Error-Signal')
  		(error, debug) = message.parse_error()
  		print('Error-Details: #%u: %s' % (error.code, debug))
  		sys.exit(1)
  
  def main():
  	signal.signal(signal.SIGINT, signal.SIG_DFL)
  
  	src = Source()
  
  	mainloop = GObject.MainLoop()
  	try:
  		mainloop.run()
  	except KeyboardInterrupt:
  		print('Terminated via Ctrl-C')
  
  
  if __name__ == '__main__':
  	main()
  
subject: remove unnecessary slashes