Clarify error message on shell command fail

Now:

# ./run project
./gitlab-ci-multi-runner run --config /home/centos/deploy-runner/net-pastis-dev-ovh-shell-new/config.toml
Traceback (most recent call last):
  File "./run", line 37, in <module>
    main()
  File "./run", line 28, in main
    subprocess.check_call(shlex.split(run_command))
  File "/usr/lib64/python2.7/subprocess.py", line 537, in check_call
    retcode = call(*popenargs, **kwargs)
  File "/usr/lib64/python2.7/subprocess.py", line 524, in call
    return Popen(*popenargs, **kwargs).wait()
  File "/usr/lib64/python2.7/subprocess.py", line 711, in __init__
    errread, errwrite)
  File "/usr/lib64/python2.7/subprocess.py", line 1327, in _execute_child
    raise child_exception

Goal, catch exception and print error message