[FEAT] add Triage/Maintain permission (#2467)

Octokit.Tests.Conventions/Exception/ResponseModelSetterlessAutoPropertyException.cs

@@ -0,0 +1,22 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Reflection;
+
+namespace Octokit.Tests.Conventions
+{
+    public class ResponseModelSetterlessAutoPropertyException : Exception
+    {
+        public ResponseModelSetterlessAutoPropertyException(Type modelType, IEnumerable<PropertyInfo> setterlessProperties)
+            : base(CreateMessage(modelType, setterlessProperties))
+        { }
+
+        static string CreateMessage(Type modelType, IEnumerable<PropertyInfo> setterlessProperties)
+        {
+            return string.Format("Model type '{0}' contains the following setterless properties: {1}{2}",
+                modelType.FullName,
+                Environment.NewLine,
+                string.Join(Environment.NewLine, setterlessProperties.Select(x => x.Name)));
+        }
+    }
+}