hack/boilerplate.sh does not work on systems without python2 yet returns success

[andreasf]

Actual behavior

hack/boilerplate.sh relies on python2, which is no longer included in modern distributions. When running the shell script, the call to python fails but the script returns a zero exit code.

user@debian:~/go/src/github.com/andreasf/kaniko$ make test
...
RUN /home/user/go/src/github.com/andreasf/kaniko/scripts/../hack/boilerplate.sh
/home/user/go/src/github.com/andreasf/kaniko/scripts/../hack/boilerplate.sh: line 22: python: command not found
PASSED /home/user/go/src/github.com/andreasf/kaniko/scripts/../hack/boilerplate.sh

user@debian:~/go/src/github.com/andreasf/kaniko$ ./hack/boilerplate.sh; echo $?
./hack/boilerplate.sh: line 22: python: command not found
0

Expected behavior
The script should return a non-zero exit code if calling python fails.

The script should call python3, because python2 will soon be removed from Github Actions Ubuntu images used in CI: actions/runner-images#7402

To Reproduce
Steps to reproduce the behavior:

1. Checkout repository on a system without python2 (e.g. Debian 12)
2. Run ./hack/boilerplate.sh, observe error message and exit code
3. Run make test, observe that it passes despite the error