A problom about CI

I built python CI on my repro to check PR last month and it worked well. But yesterday it didn’t work with the feedback “Error: Process completed with exit code 127”. I didn’t change my testing code and my testing code work well on my machine. What’s more, I just changed my README.md and made a PR to test the CI, and it still report the same error. I don’t know if the update of Github causes this problem, is there anyone can help me or having same problem?