Ask user for path to an image. Convert it to grayscale and save it as 'gray.png'.
ImportError: No module named Crypto.Cipher
You need to install the cryptography library. You might have installed it in a different location. Try doing "pip3 install cryptography" or "pip install cryptography" depending on your python version and OS. Make sure that you are using the correct path for your installation of cryptography, if you have multiple installations of Python/cryptography in different locations, try adding them all to sys.path so that they can be found by import statements.