I have had the same error.
On September 7 the cryptography library was updated from version 37.0.4 to version 38.0.1, so the PGPy module is misaligned.
To fix this:
- Remove the PGPy module via pip command
- Install the cryptography module to the previous version "pip install cryptography == 37.0.4"
- Install the PGPy module again.
This should temporarily fix the problem, until they update the PGPy library.
I hope I have been of help to you.