API Error page support for Security controller errors

_config/config.yml

@@ -1,3 +1,6 @@
 LeftAndMain:
   extensions:
-    - LeftAndMainPageIconsExtension
+    - LeftAndMainPageIconsExtension
+Security:
+  extensions:
+    - ErrorPageControllerExtension

code/controllers/ErrorPageControllerExtension.php

@@ -0,0 +1,17 @@
+<?php
+
+/**
+ * Enhances error handling for a controller with ErrorPage generated output
+ * 
+ * @package cms
+ * @subpackage controller
+ */
+class ErrorPageControllerExtension extends Extension {
+
+	public function onBeforeHTTPError($statusCode, $request) {
+		$response = ErrorPage::response_for($statusCode);
+		if($response) {
+			throw new SS_HTTPResponse_Exception($response, $statusCode);
+		}
+	}
+}

tests/model/ErrorPageTest.php

@@ -70,4 +70,16 @@ public function testBehaviourOf403() {
 		$this->assertEquals($response->getStatusCode(), '403');
 		$this->assertNotNull($response->getBody(), 'We have body text from the error page');
 	}
-}
+
+	public function testSecurityError() {
+		// Generate 404 page
+		$page = $this->objFromFixture('ErrorPage', '404');
+		$page->publish('Stage', 'Live');
+
+		// Test invalid action
+		$response = $this->get('Security/nosuchaction');
+		$this->assertEquals($response->getStatusCode(), '404');
+		$this->assertNotNull($response->getBody());
+		$this->assertContains('text/html', $response->getHeader('Content-Type'));
+	}
+}