- Patch #35926 by asimmonds: make required vocabularies actually required.

modules/taxonomy.module

@@ -533,6 +533,7 @@ function taxonomy_form_alter($form_id, &$form) {
       else {
         $form['taxonomy'][$vocabulary->vid] = taxonomy_form($vocabulary->vid, array_keys($terms), $help);
         $form['taxonomy'][$vocabulary->vid]['#weight'] = $vocabulary->weight;
+        $form['taxonomy'][$vocabulary->vid]['#required'] = $vocabulary->required;
       }
     }
     if (isset($form['taxonomy'])) {

modules/taxonomy/taxonomy.module

@@ -533,6 +533,7 @@ function taxonomy_form_alter($form_id, &$form) {
       else {
         $form['taxonomy'][$vocabulary->vid] = taxonomy_form($vocabulary->vid, array_keys($terms), $help);
         $form['taxonomy'][$vocabulary->vid]['#weight'] = $vocabulary->weight;
+        $form['taxonomy'][$vocabulary->vid]['#required'] = $vocabulary->required;
       }
     }
     if (isset($form['taxonomy'])) {