ERROR: Could not build wheels for cryptography which use PEP 517 and cannot be installed directly

Setting cryptography to version 2.8 in requirements.txt fixed the issue.

TLDR;

Try using cryptography==3.1.1

Details:

This happened on Python 3.9.0 on Windows 10 PC. I had the following in requirements.txt

cryptography==2.8

I removed the version and kept only cryptography in requirements.txt file like below

cryptography

Saved the requirements.txt and then I ran

pip install -r requirements.txt

It installed successfully. Then I freeze the requirements.txt by running the following command

pip freeze > requirements.txt

Then the requirements.txt got updated with cryptography==3.1.1

In my case (windows 10 + conda) updating pip fixed the problem:

python -m pip install --upgrade pip