i did a bit of debugging and figured out which line in your code is causing the segfault.

line 80 -> fin,fout = os.popen4(ListCmd)

that line causes the segfault. ListCmd shows a value of "/opt/gngeo/bin/gngeo --scandir=/home/user/MyDocs/roms/neogeo"
when i run that command from the command line, the scandir works fine and neogeo finds all the roms i have in that folder.