Make error response and actual 500 http status

AchmeErrorSite/AchmeErrorSite.csproj

@@ -465,6 +465,7 @@
   <ItemGroup>
     <Compile Include="AchmeClass.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
+    <Compile Include="SiteApplication.cs" />
   </ItemGroup>
   <ItemGroup>
     <Analyzer Include="..\packages\Microsoft.CodeAnalysis.Analyzers.1.1.0\analyzers\dotnet\cs\Microsoft.CodeAnalysis.Analyzers.dll" />

AchmeErrorSite/App_Data/Models/all.dll.path

@@ -1 +1 @@
-C:\Windows\Microsoft.NET\Framework\v4.0.30319\Temporary ASP.NET Files\vs\75441ed1\d5440aaf\App_Web_all.generated.cs.8f9494c4.z-ucklgj.dll
+C:\Windows\Microsoft.NET\Framework\v4.0.30319\Temporary ASP.NET Files\vs\75441ed1\d5440aaf\App_Web_all.generated.cs.8f9494c4.9mgasjtp.dll

AchmeErrorSite/Global.asax

@@ -1,2 +1,2 @@
-<%@ Application Inherits="Umbraco.Web.UmbracoApplication" Language="C#" %>
+<%@ Application Inherits="AchmeErrorSite.SiteApplication" Language="C#" %>
 

AchmeErrorSite/SiteApplication.cs

@@ -0,0 +1,36 @@
+using System;
+using System.Web;
+using Umbraco.Web;
+
+namespace AchmeErrorSite
+{
+	public class SiteApplication : UmbracoApplication
+	{
+		protected new void Application_Error(object sender, EventArgs e)
+		{
+			// This method is triggered twice when an exception occurs.
+			// Only do anything if there is actually an error.
+			// Otherwise just ignore it.
+
+			Exception lastError = Server.GetLastError();
+
+			if (lastError != null)
+			{
+				base.Application_Error(sender, e);
+			}
+
+			if (Context.IsCustomErrorEnabled)
+			{
+				if (lastError != null)
+				{
+					var httpException = lastError as HttpException ?? new HttpException(500, "Internal error");
+
+					var code = httpException.GetHttpCode();
+					Response.StatusCode = code;
+					Server.ClearError();
+					Server.Transfer("/500.html");
+				}
+			}
+		}
+	}
+}

AchmeErrorSite/Web.config

@@ -87,7 +87,7 @@
 	</system.net>
 
 	<system.web>
-		<customErrors mode="On" defaultRedirect="/500.html" redirectMode="ResponseRewrite" />
+		<customErrors mode="On" />
 		<trace enabled="false" requestLimit="10" pageOutput="false" traceMode="SortByTime" localOnly="true" />
 		<httpRuntime requestValidationMode="2.0" enableVersionHeader="false" targetFramework="4.5" maxRequestLength="51200" fcnMode="Single" />
 		<!--