Comment by Joker_vD
But the sl is not invoked by you. It is invoked by some npm module (a 5-times-removed dependency from any side) which hopes that either there is "sl" in the $PATH and it is the Sapling CLI, or there is no "sl" in the $PATH. This module can't use absolute paths because it does not know how the end user's system looks.
In that case it is a large security risk as well as it does not work as per the article