Can't read /var/mail/tweetutilities

Just had a complete brain fart and am hoping I can save someone else from suffering the same. I’m following an O-Reilly tutorial about using the Twitter API and I’m running a simple from tweetutilities import print_tweet in the terminal. But the output - from: can't read /var/mail/tweetutilities is making absolutely no sense to me. Googling doesn’t turn anything meaningful up. I’ve never dealt with /var/mail before and while someone else wrote the file, neither a search in VSCode nor my own perusing of the file showed anything that would’ve called /var/mail.

It wasn’t until I took a break and came back and realized that I wasn’t in the python REPL, where the command was supposed to be typed. So try….

python3 … and then…. from tweetutilities import print_tweet