When I setup some maintenance scripts, I needed to copy some files from our CPanel servers to a central server for processing.
After it was all setup, I discovered the server was sending an email with every crontab on the central server that only had one line of text:
stdin: is not a tty
After some research, I found the solution was to add the following to the beginning of the ~/.bashrc file:
# If not running interactively, don't do anything
case $- in
*i*) ;;
*) return;;
esac