Add missing period.

Test app files were inconsistently using `.` on this message string
causing duplicate entries in generate POT files.

Fixes #6312

tests/TestCase/Error/ErrorHandlerTest.php

@@ -338,7 +338,7 @@ class ErrorHandlerTest extends TestCase
         $result = $errorHandler->response->body();
         $this->assertNotContains('Something wrong', $result, 'message must not appear.');
         $this->assertNotContains(__FILE__, $result, 'filename must not appear.');
-        $this->assertContains('An Internal Error Has Occurred', $result);
+        $this->assertContains('An Internal Error Has Occurred.', $result);
     }
 
     /**

tests/TestCase/Error/ExceptionRendererTest.php

@@ -461,7 +461,7 @@ class ExceptionRendererTest extends TestCase
         $ExceptionRenderer->controller->response->expects($this->once())->method('statusCode')->with(500);
 
         $result = $ExceptionRenderer->render();
-        $this->assertContains('<h2>An Internal Error Has Occurred</h2>', $result->body());
+        $this->assertContains('<h2>An Internal Error Has Occurred.</h2>', $result->body());
         $this->assertContains('An Internal Error Has Occurred.</p>', $result->body());
     }
 

tests/test_app/TestApp/Template/Error/error500.ctp

@@ -14,7 +14,7 @@
  */
 use Cake\Core\Configure;
 ?>
-<h2><?= __d('cake', 'An Internal Error Has Occurred') ?></h2>
+<h2><?= __d('cake', 'An Internal Error Has Occurred.') ?></h2>
 <p class="error">
     <strong><?= __d('cake', 'Error') ?>: </strong>
     <?= h($message) ?>