Use a different exception type.

src/VisualStudio/Core/Def/Implementation/ProjectSystem/VisualStudioWorkspaceImpl.cs

@@ -677,7 +677,7 @@ public void OpenDocumentCore(DocumentId documentId, bool activate = true)
 
             if (!foregroundObject.IsForeground())
             {
-                throw new NotSupportedException(ServicesVSResources.ThisWorkspaceOnlySupportsOpeningDocumentsOnTheUIThread);
+                throw new InvalidOperationException(ServicesVSResources.ThisWorkspaceOnlySupportsOpeningDocumentsOnTheUIThread);
             }
 
             var document = this.GetHostDocument(documentId);