AM6412: Optee-os Compilation Issue

Hi all,

I am facing this issue while compiling the optee_os package,

GEN out/arm-plat-k3/core/ta_pub_key.c
Traceback (most recent call last):
File "scripts/pem_to_pub_c.py", line 71, in <module>
main()
File "scripts/pem_to_pub_c.py", line 24, in main
from cryptography.hazmat.backends import default_backend
ModuleNotFoundError: No module named 'cryptography'
mk/subdir.mk:183: recipe for target 'out/arm-plat-k3/core/ta_pub_key.c' failed
make: *** [out/arm-plat-k3/core/ta_pub_key.c] Error 1

i have followed these steps 

https://software-dl.ti.com/processor-sdk-linux/esd/AM64X/08_04_01_04/exports/docs/linux/Foundational_Components_OPTEE.html

i am also referred this thread 

https://e2e.ti.com/support/processors-group/processors/f/processors-forum/1097588/am6442-errors-while-building-optee

But this doesn't work for me,Can anyone suggest some steps to over come this issue?