Install cl-trivial-gray-streams by entering the following commands in the terminal:
sudo apt update sudo apt install cl-trivial-gray-streams
thin compatibility layer for gray streams
This system provides an extremely thin compatibility layer for gray streams. It is nearly *too* trivial for a complete package, except that the author has copy&pasted this code into enough projects now that the author decided to factor it out once again now, and then *never* have to touch it again.