To validate that the docker gpg key is installed, I ran:
sudo apt-key fingerprint 0EBFCD88 | grep "9DC8 5822 9FC7 DD38 854A E2D8 8D81 803C 0EBF CD88"
Which resulted in the following output:
Warning: apt-key output should not be parsed (stdout is not a terminal)
9DC8 5822 9FC7 DD38 854A E2D8 8D81 803C 0EBF CD88
I found this Stack Overflow question on how to circumvent the warning, but I couldn't find any sources on why it appears in the first place? What's the reason you shouldn't parse apt-key output?