[IronPython] No module named System

[Hello Sticky]

Hi, I'm dynamically loading a python assembly built through pyc.py
into a partially trusted AppDomain. First, the exception, and after
that follows the code I'm using. The question is: how do I need to add
a reference to System.dll -- through runtime.LoadAssembly,
clr.AddReference, or both?

IronPython.Runtime.Exceptions.ImportException: "No module named System"
   at IronPython.Runtime.Builtin.__import__(CodeContext context,
String name, Object globals, Object locals, Object fromlist, Int32
level)
   at IronPython.Runtime.Builtin.__import__(CodeContext context,
String name, Object globals, Object locals, Object fromlist)
   at _stub_$20##20(Closure , CallSite , CodeContext , Object , String
, IAttributesCollection , IAttributesCollection , PythonTuple )
... long stack trace

Loading code:

Assembly assembly = Assembly.Load(AssemblyName);
                    ScriptRuntimeSetup setup = new ScriptRuntimeSetup();
                    setup.LanguageSetups.Add(Python.CreateLanguageSetup(null));
                    ScriptRuntime runtime = new ScriptRuntime(setup);
                    runtime.LoadAssembly(assembly);
                    runtime.IO.SetOutput(ms, writer);
                    ScriptEngine engine = runtime.GetEngine(GetEngineName());
                    ScriptScope scope = engine.CreateScope();

                    string code = string.Format(@"import clr
clr.AddReference(""{0}"")
import {1}
",
     AssemblyName,
     AssemblyType.Replace(".py", "")
     );
                    ScriptSource source = engine.CreateScriptSourceFromString(
                        code,
                        SourceCodeKind.Statements
                    );
                    source.Execute(scope);

Thanks,