In this step your goal is to handle non-existent commands.

Now that we can enter multiple commands and safely exit our shell, we want to ensure it is robust. That is, if the user tries to run a command that doesn’t exist our shell shouldn’t crash.

That should look something like this when it’s done:

% ccsh
ccsh> fubar
FileNotFoundError: [Errno 2] No such file or directory: 'fubar'
ccsh> exit
%