mod.lua

function run_my_mod()
	...
end

function OnMsg.LoadGame()
	xpcall(run_my_mod, function(err)
		WaitCustomPopupNotification(
			'ERROR when running mod',
			string.format('----- Details:\n%s\n%s\n----- :end\n', err, debug.traceback()),
			{'Oops!'})
		return false
	end)
end