Hello djrevmoon,
I see in your code that you are executing "./gsm_receive_rtl.py", I installed airprobe and is working with GNURadio 3.7 and BladeRF, but I call the python script provided in the airprobe-3.7-hackrf-patch:
"gsm_receive_hackrf_3.7.py"
Hackrf and BladeRF are handled by gr-osmosdr, so this script works for both boards.
Let me know if this helps you.
KR,
Pedro