Issue #2097537 by tim.plunkett: Fixed Random failure in...

Issue #2097537 by tim.plunkett: Fixed Random failure in Drupal\block\Tests\Views\DisplayBlockTest->testBlockCategory().

core/modules/block/lib/Drupal/block/Tests/Views/DisplayBlockTest.php

@@ -95,7 +95,7 @@ public function testBlockCategory() {
     $this->drupalPostForm(NULL, array(), t('Save'));
 
     // Test that the blocks are listed under the correct categories.
-    $category_id = 'edit-' . drupal_html_id(String::checkPlain($category));
+    $category_id = drupal_html_id('edit-' . String::checkPlain($category));
     $arguments[':id'] = $category_id;
     $this->drupalGet('admin/structure/block');
     $elements = $this->xpath('//details[@id=:id]//li[contains(@class, :li_class)]/a[contains(@href, :href) and text()=:text]', $arguments);