-e: see title. while it is not officially supported it worked before thus a regression on our end.
--works in 2017.2, .3, .4
--stops working in 2018.1.x

-repro:
--open attached project
--open sample scene
--press play
--notice the the logging in the console
--build and run WebGL
--open browser console
--NOTICE exceptions being thrown (none thrown in 2017.4 and before)