To setup your keychain run the following in your shell
security add-generic-password -a AWS_SECRET_KEY -s foo.bar -w foo
security add-generic-password -a AWS_ACCESS_KEY -s foo.bar -w bar
To remove the keychain items run
security delete-generic-password -a AWS_SECRET_KEY -s foo.bar
security delete-generic-password -a AWS_ACCESS_KEY -s foo.bar