The ScriptUtil.LoadAssemblyFromUrl method was marked obsolete in v10.2.1.0 HF32. A workaround for M3 scripts using the method is to replace with the following code:
var assembly = Assembly.Load(WebReader.GetRequestBinary(url));
In between version 10.2.1.0.333 (HF32) and 10.2.1.0.385 (HF42) the obsolete method will
fail in silence and just return null.
This has been changed in 10.2.1.0.389 (HF43) and an InvalidOperationException will be thrown when calling the method.