Error in executing the example of mesh networks ns-3

[Fernando Sousa]

Hello guys, 

I'm trying to do a job simulation with NS-3 (especially related to mesh networks), but when running the sample script in NS it reports the following error: 

"Could not load icon due to missing Python module gnomedesktop applets-screenshooter 

assert failed. cond = "m_metadataSkipped!", msg = "Error: Attempting to enable the packet metadata subsystem too late in the simulation, Which Is not allowed. 

A common cause for this problem is to enable ASCII tracing after sending any packets. One way to fix this problem is to call ns3 :: PacketMetadata :: Enable () near the beginning of the program, before any packets are sent. ", File = .. / src / network / model / packet-metadata.cc, line = 61 

terminate called without an active exception 

Command ['/home/zeus/Downloads/ns-allinone-3.21/ns-3.21/build/src/mesh/examples/ns3.21-mesh-debug', '--SimulatorImplementationType = ns3 :: VisualSimulatorImpl'] terminated with SIGIOT signal. Run it under the debugger to get more information (./waf --run <program> --command-template = "gdb% s --args <args>"). "

Could someone help me with this? 

PS: I am a beginner in the tool.