Use GetExportedTypes where possible and filter nested types

This is basically what @dmitriyse prepared in PR 528 without the event code that I don't understand.
pythonnet · filmor · Nov 14, 2018 · Aug 21, 2018 · Aug 24, 2018 · Oct 16, 2018
commit 8a88a18ef23330c513fcfad986ece7b7b4ed7318
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -8,6 +8,7 @@ This document follows the conventions laid out in [Keep a CHANGELOG][].
 ## [unreleased][]
 
 ### Added
+
 -   Added support for embedding python into dotnet core 2.0 (NetStandard 2.0)
 -   Added new build system (pythonnet.15.sln) based on dotnetcore-sdk/xplat(crossplatform msbuild).
     Currently there two side-by-side build systems that produces the same output (net40) from the same sources.
@@ -36,6 +37,7 @@ This document follows the conventions laid out in [Keep a CHANGELOG][].
 -   Fixed errors breaking .NET Remoting on method invoke ([#276][i276])
 -   Fixed PyObject.GetHashCode ([#676][i676])
 -   Fix memory leaks due to spurious handle incrementation ([#691][i691])
+-   Fix spurious assembly loading exceptions from private types ([#703][i703])
 
 
 ## [2.3.0][] - 2017-03-11

diff --git a/src/runtime/assemblymanager.cs b/src/runtime/assemblymanager.cs
@@ -343,9 +343,7 @@ internal static void ScanAssembly(Assembly assembly)
             // A couple of things we want to do here: first, we want to
             // gather a list of all of the namespaces contributed to by
             // the assembly.
-
-            Type[] types = assembly.GetTypes();
-            foreach (Type t in types)
+            foreach (Type t in GetTypes(assembly))
             {
                 string ns = t.Namespace ?? "";
                 if (!namespaces.ContainsKey(ns))
@@ -419,10 +417,9 @@ public static List<string> GetNames(string nsname)
             {
                 foreach (Assembly a in namespaces[nsname].Keys)
                 {
-                    Type[] types = a.GetTypes();
-                    foreach (Type t in types)
+                    foreach (Type t in GetTypes(a))
                     {
-                        if ((t.Namespace ?? "") == nsname)
+                        if ((t.Namespace ?? "") == nsname && !t.IsNested)
                         {
                             names.Add(t.Name);
                         }
@@ -461,5 +458,13 @@ public static Type LookupType(string qname)
             }
             return null;
         }
+
+        internal static Type[] GetTypes(Assembly a)
+        {
+            if (a.IsDynamic)
+                return a.GetTypes();
+            else
+                return a.GetExportedTypes();
+        }
     }
 }