```
 0:27.48 pid:4157 Traceback (most recent call last):
 0:27.48 pid:4157   File "/home/simon/servo1/etc/run_in_headless_android_emulator.py", line 212, in <module>
 0:27.48 pid:4157     sys.exit(main(*sys.argv[1:]))
 0:27.48 pid:4157   File "/home/simon/servo1/etc/run_in_headless_android_emulator.py", line 72, in main
 0:27.48 pid:4157     forward_webdriver(adb, args)
 0:27.48 pid:4157   File "/home/simon/servo1/etc/run_in_headless_android_emulator.py", line 163, in forward_webdriver
 0:27.48 pid:4157     ports = [int(part) for part in split if part]
 0:27.48 pid:4157 ValueError: invalid literal for int() with base 10: 'None'
```