[PROBLEM] Installing python modules fails

[postcd]

When i "apt install libffi-dev", it still shows error output, this time for pysha3.
After searching for pysha3 debian package, found it may be package "python3-sha3":

sudo apt install python*sha3
Then the "pip install merkletools" succeeded without any error.

Both packages 300kB of data extracted.

But after running "pip install -r ./requirements.txt" cffi error output still there, so after searching "cffi python3 package debian" installed "sudo apt install python3-cffi"

cffi error remains as seen in this output of pip install command.

$ sudo python3 -m pip install cffi
Requirement already satisfied: cffi in /usr/lib/python3/dist-packages (1.14.5)