fix issue with alias usage in core lib function split_string (#7)
fix issue with alias usage in core lib function split_string (#7)

* fix issue with alias usage in core lib function split_string

split_string was using athena.exit_with_msg but it should not use
aliases inside the core lib functions and also the alias seems to be not
existing at the time of call, so athena.exit_with_msg failed

* better use internal test methods

athena-oss/athena