Updated error boundary for prompt generation endpoint and tests

fuel/app/classes/materia/api/v1.php

@@ -896,7 +896,7 @@ static public function question_set_generate($inst_id, $widget_id, $topic, $incl
 
 	static public function widget_prompt_generate($prompt)
 	{
-		if ( ! Widget_Question_Generator::is_enabled()) throw new \HttpNotFoundException;
+		if ( ! Widget_Question_Generator::is_enabled()) return Msg::failure();
 		if (\Service_User::verify_session() !== true) return Msg::no_login();
 
 		$result = Widget_Question_Generator::generate_from_prompt($prompt);

fuel/app/tests/api/v1.php

@@ -1174,28 +1174,14 @@ public function test_widget_prompt_generate()
 	{
 		if ( ! \Materia\Widget_Question_Generator::is_enabled())
 		{
-			try
-			{
-				$output = Api_V1::widget_prompt_generate('Provide a background story for Kogneato, the robot mascot of Materia, a platform for educational tools and games.');
-				$this->fail('Expected exception HttpNotFoundException not thrown');
-			}
-			catch (\Exception $e)
-			{
-				$this->assertInstanceOf('HttpNotFoundException', $e);
-			}
+			$output = Api_V1::widget_prompt_generate('Provide a background story for Kogneato, the robot mascot of Materia, a platform for educational tools and games.');
+			$this->assert_failure_message($output);
 		}
 		else
 		{
 			// ======= AS NO ONE ========
-			try
-			{
-				$output = Api_V1::widget_prompt_generate('Provide a background story for Kogneato, the robot mascot of Materia, a platform for educational tools and games.');
-				$this->fail('Expected exception HttpNotFoundException not thrown');
-			}
-			catch (\Exception $e)
-			{
-				$this->assertInstanceOf('HttpNotFoundException', $e);
-			}
+			$output = Api_V1::widget_prompt_generate('Provide a background story for Kogneato, the robot mascot of Materia, a platform for educational tools and games.');
+			$this->assert_invalid_login_message($output);
 		}
 	}