require("gsl"); replaced by require( "gsl" );, which prevents it being removed...

require("gsl"); replaced by require( "gsl" );, which prevents it being removed by bin/makestatic_isiscripts

bin/makestatic_isiscripts removes require(feature); statements if the feature has already been required before.
This behavior is not desired when the presence of external modules is to be checked in a try-block.