Open class scope when getting value from ctor (microsoft#926)

Found in microsoft#923.

Is there an easy way to test this, or is this alright as-is?

Author: jakebailey

src/Analysis/Ast/Impl/Analyzer/Evaluation/ExpressionEval.Callables.cs

@@ -89,11 +89,13 @@ public IMember GetValueFromClassCtor(IPythonClassType cls, CallExpression expr)
             var args = ArgumentSet.Empty;
             var init = cls.GetMember<IPythonFunctionType>(@"__init__");
             if (init != null) {
-                var a = new ArgumentSet(init, 0, new PythonInstance(cls), expr, Module, this);
-                if (a.Errors.Count > 0) {
-                    // AddDiagnostics(Module.Uri, a.Errors);
+                using (OpenScope(cls.DeclaringModule, cls.ClassDefinition, out _)) {
+                    var a = new ArgumentSet(init, 0, new PythonInstance(cls), expr, Module, this);
+                    if (a.Errors.Count > 0) {
+                        // AddDiagnostics(Module.Uri, a.Errors);
+                    }
+                    args = a.Evaluate();
                 }
-                args = a.Evaluate();
             }
             return cls.CreateInstance(cls.Name, args);
         }