Merge pull request #4425 from magento-obsessive-owls/MC-17814

Author: danmooney2

app/code/Magento/Backend/view/adminhtml/templates/widget/form/renderer/fieldset.phtml

@@ -53,6 +53,9 @@ if ($isField) {
 
     <?php if (!$element->getNoContainer()) : ?>
         <fieldset class="<?=  $block->escapeHtmlAttr($cssClass) ?>" id="<?=  $block->escapeHtmlAttr($id) ?>">
+        <?php if (strlen($element->getBeforeElementHtml())) : ?>
+            <?= $element->getBeforeElementHtml() ?>
+        <?php endif ?>
         <?php if ($element->getLegend() && !$isWrapped) : ?>
             <legend class="<?= /* @noEscape */ $isField ? 'label admin__field-label' : 'admin__legend legend' ?>">
                 <span><?= $block->escapeHtml($element->getLegend()) ?></span>

app/code/Magento/Widget/Block/Adminhtml/Widget/Form.php

@@ -11,6 +11,9 @@
  */
 namespace Magento\Widget\Block\Adminhtml\Widget;
 
+/**
+ * Widget Form Block class
+ */
 class Form extends \Magento\Backend\Block\Widget\Form\Generic
 {
     /**
@@ -47,8 +50,13 @@ protected function _prepareForm()
         $form = $this->_formFactory->create();
 
         // Add messages container to fieldset
-        $fieldset = $form->addFieldset('base_fieldset', ['legend' => '<div data-role="messages"></div>',
-            'comment' => __('Inserting a widget does not create a widget instance.')]);
+        $fieldset = $form->addFieldset(
+            'base_fieldset',
+            [
+                'before_element_html' => '<div data-role="messages"></div>',
+                'comment' => __('Inserting a widget does not create a widget instance.'),
+            ]
+        );
 
         $fieldset->addField(
             'select_widget_type',