Slight Changes to Code

app/code/Magento/Cms/Controller/Adminhtml/Block/Delete.php

@@ -26,18 +26,18 @@ public function execute()
                 $model->load($id);
                 $model->delete();
                 // display success message
-                $this->messageManager->addSuccess(__('You deleted the block.'));
+                $this->messageManager->addSuccessMessage(__('You deleted the block.'));
                 // go to grid
                 return $resultRedirect->setPath('*/*/');
             } catch (\Exception $e) {
                 // display error message
-                $this->messageManager->addError($e->getMessage());
+                $this->messageManager->addErrorMessage($e->getMessage());
                 // go back to edit form
                 return $resultRedirect->setPath('*/*/edit', ['block_id' => $id]);
             }
         }
         // display error message
-        $this->messageManager->addError(__('We can\'t find a block to delete.'));
+        $this->messageManager->addErrorMessage(__('We can\'t find a block to delete.'));
         // go to grid
         return $resultRedirect->setPath('*/*/');
     }

app/code/Magento/Cms/Controller/Adminhtml/Block/Edit.php

@@ -42,7 +42,7 @@ public function execute()
         if ($id) {
             $model->load($id);
             if (!$model->getId()) {
-                $this->messageManager->addError(__('This block no longer exists.'));
+                $this->messageManager->addErrorMessage(__('This block no longer exists.'));
                 /** @var \Magento\Backend\Model\View\Result\Redirect $resultRedirect */
                 $resultRedirect = $this->resultRedirectFactory->create();
                 return $resultRedirect->setPath('*/*/');

app/code/Magento/Cms/Controller/Adminhtml/Block/InlineEdit.php

@@ -46,6 +46,7 @@ public function __construct(
 
     /**
      * @return \Magento\Framework\Controller\ResultInterface
+     * @throws \Magento\Framework\Exception\LocalizedException
      */
     public function execute()
     {

app/code/Magento/Cms/Controller/Adminhtml/Block/MassDelete.php

@@ -60,7 +60,7 @@ public function execute()
             $block->delete();
         }
 
-        $this->messageManager->addSuccess(__('A total of %1 record(s) have been deleted.', $collectionSize));
+        $this->messageManager->addSuccessMessage(__('A total of %1 record(s) have been deleted.', $collectionSize));
 
         /** @var \Magento\Backend\Model\View\Result\Redirect $resultRedirect */
         $resultRedirect = $this->resultFactory->create(ResultFactory::TYPE_REDIRECT);

app/code/Magento/Cms/Controller/Adminhtml/Page/Delete.php

@@ -26,35 +26,42 @@ public function execute()
         $id = $this->getRequest()->getParam('page_id');
         /** @var \Magento\Backend\Model\View\Result\Redirect $resultRedirect */
         $resultRedirect = $this->resultRedirectFactory->create();
+
         if ($id) {
             $title = "";
             try {
                 // init model and delete
                 $model = $this->_objectManager->create(\Magento\Cms\Model\Page::class);
                 $model->load($id);
+
                 $title = $model->getTitle();
                 $model->delete();
+
                 // display success message
-                $this->messageManager->addSuccess(__('The page has been deleted.'));
+                $this->messageManager->addSuccessMessage(__('The page has been deleted.'));
+
                 // go to grid
-                $this->_eventManager->dispatch(
-                    'adminhtml_cmspage_on_delete',
-                    ['title' => $title, 'status' => 'success']
-                );
+                $this->_eventManager->dispatch('adminhtml_cmspage_on_delete', [
+                    'title' => $title,
+                    'status' => 'success'
+                ]);
+
                 return $resultRedirect->setPath('*/*/');
             } catch (\Exception $e) {
                 $this->_eventManager->dispatch(
                     'adminhtml_cmspage_on_delete',
                     ['title' => $title, 'status' => 'fail']
                 );
                 // display error message
-                $this->messageManager->addError($e->getMessage());
+                $this->messageManager->addErrorMessage($e->getMessage());
                 // go back to edit form
                 return $resultRedirect->setPath('*/*/edit', ['page_id' => $id]);
             }
         }
+
         // display error message
-        $this->messageManager->addError(__('We can\'t find a page to delete.'));
+        $this->messageManager->addErrorMessage(__('We can\'t find a page to delete.'));
+
         // go to grid
         return $resultRedirect->setPath('*/*/');
     }

app/code/Magento/Cms/Controller/Adminhtml/Page/Edit.php

@@ -76,7 +76,7 @@ public function execute()
         if ($id) {
             $model->load($id);
             if (!$model->getId()) {
-                $this->messageManager->addError(__('This page no longer exists.'));
+                $this->messageManager->addErrorMessage(__('This page no longer exists.'));
                 /** \Magento\Backend\Model\View\Result\Redirect $resultRedirect */
                 $resultRedirect = $this->resultRedirectFactory->create();
                 return $resultRedirect->setPath('*/*/');

app/code/Magento/Cms/Controller/Adminhtml/Page/InlineEdit.php

@@ -57,6 +57,7 @@ public function __construct(
 
     /**
      * @return \Magento\Framework\Controller\ResultInterface
+     * @throws \Magento\Framework\Exception\LocalizedException
      */
     public function execute()
     {

app/code/Magento/Cms/Controller/Adminhtml/Page/MassDelete.php

@@ -59,10 +59,11 @@ public function execute()
             $page->delete();
         }
 
-        $this->messageManager->addSuccess(__('A total of %1 record(s) have been deleted.', $collectionSize));
+        $this->messageManager->addSuccessMessage(__('A total of %1 record(s) have been deleted.', $collectionSize));
 
         /** @var \Magento\Backend\Model\View\Result\Redirect $resultRedirect */
         $resultRedirect = $this->resultFactory->create(ResultFactory::TYPE_REDIRECT);
+
         return $resultRedirect->setPath('*/*/');
     }
 }

app/code/Magento/Cms/Controller/Adminhtml/Page/MassDisable.php

@@ -59,7 +59,9 @@ public function execute()
             $item->save();
         }
 
-        $this->messageManager->addSuccess(__('A total of %1 record(s) have been disabled.', $collection->getSize()));
+        $this->messageManager->addSuccessMessage(
+            __('A total of %1 record(s) have been disabled.', $collection->getSize())
+        );
 
         /** @var \Magento\Backend\Model\View\Result\Redirect $resultRedirect */
         $resultRedirect = $this->resultFactory->create(ResultFactory::TYPE_REDIRECT);

app/code/Magento/Cms/Controller/Adminhtml/Page/MassEnable.php

@@ -59,7 +59,9 @@ public function execute()
             $item->save();
         }
 
-        $this->messageManager->addSuccess(__('A total of %1 record(s) have been enabled.', $collection->getSize()));
+        $this->messageManager->addSuccessMessage(
+            __('A total of %1 record(s) have been enabled.', $collection->getSize())
+        );
 
         /** @var \Magento\Backend\Model\View\Result\Redirect $resultRedirect */
         $resultRedirect = $this->resultFactory->create(ResultFactory::TYPE_REDIRECT);

app/code/Magento/Cms/Controller/Adminhtml/Page/PostDataProcessor.php

@@ -119,7 +119,7 @@ public function validateRequireEntry(array $data)
         foreach ($data as $field => $value) {
             if (in_array($field, array_keys($requiredFields)) && $value == '') {
                 $errorNo = false;
-                $this->messageManager->addError(
+                $this->messageManager->addErrorMessage(
                     __('To apply changes you should fill in hidden required "%1" field', $requiredFields[$field])
                 );
             }
@@ -140,6 +140,7 @@ private function validateData($data, $layoutXmlValidator)
             if (!empty($data['layout_update_xml']) && !$layoutXmlValidator->isValid($data['layout_update_xml'])) {
                 return false;
             }
+
             if (!empty($data['custom_layout_update_xml']) &&
                 !$layoutXmlValidator->isValid($data['custom_layout_update_xml'])
             ) {

app/code/Magento/Cms/Controller/Adminhtml/Wysiwyg/Images/Index.php

@@ -39,7 +39,7 @@ public function execute()
         try {
             $this->_objectManager->get(\Magento\Cms\Helper\Wysiwyg\Images::class)->getCurrentPath();
         } catch (\Exception $e) {
-            $this->messageManager->addError($e->getMessage());
+            $this->messageManager->addErrorMessage($e->getMessage());
         }
         $this->_initAction();
         /** @var \Magento\Framework\View\Result\Layout $resultLayout */

app/code/Magento/Cms/Test/Unit/Controller/Adminhtml/Block/DeleteTest.php

@@ -134,10 +134,10 @@ public function testDeleteAction()
             ->with($this->blockId);
 
         $this->messageManagerMock->expects($this->once())
-            ->method('addSuccess')
+            ->method('addSuccessMessage')
             ->with(__('You deleted the block.'));
         $this->messageManagerMock->expects($this->never())
-            ->method('addError');
+            ->method('addErrorMessage');
 
         $this->resultRedirectMock->expects($this->once())
             ->method('setPath')
@@ -154,10 +154,10 @@ public function testDeleteActionNoId()
             ->willReturn(null);
 
         $this->messageManagerMock->expects($this->once())
-            ->method('addError')
+            ->method('addErrorMessage')
             ->with(__('We can\'t find a block to delete.'));
         $this->messageManagerMock->expects($this->never())
-            ->method('addSuccess');
+            ->method('addSuccessMessage');
 
         $this->resultRedirectMock->expects($this->once())
             ->method('setPath')
@@ -181,10 +181,10 @@ public function testDeleteActionThrowsException()
             ->willThrowException(new \Exception(__($errorMsg)));
 
         $this->messageManagerMock->expects($this->once())
-            ->method('addError')
+            ->method('addErrorMessage')
             ->with($errorMsg);
         $this->messageManagerMock->expects($this->never())
-            ->method('addSuccess');
+            ->method('addSuccessMessage');
 
         $this->resultRedirectMock->expects($this->once())
             ->method('setPath')

app/code/Magento/Cms/Test/Unit/Controller/Adminhtml/Block/EditTest.php

@@ -139,7 +139,7 @@ public function testEditActionBlockNoExists()
             ->willReturn(null);
 
         $this->messageManagerMock->expects($this->once())
-            ->method('addError')
+            ->method('addErrorMessage')
             ->with(__('This block no longer exists.'));
 
         $this->resultRedirectFactoryMock->expects($this->atLeastOnce())

app/code/Magento/Cms/Test/Unit/Controller/Adminhtml/Block/MassDeleteTest.php

@@ -68,9 +68,9 @@ public function testMassDeleteAction()
             ->willReturn(new \ArrayIterator($collection));
 
         $this->messageManagerMock->expects($this->once())
-            ->method('addSuccess')
+            ->method('addSuccessMessage')
             ->with(__('A total of %1 record(s) have been deleted.', $deletedBlocksCount));
-        $this->messageManagerMock->expects($this->never())->method('addError');
+        $this->messageManagerMock->expects($this->never())->method('addErrorMessage');
 
         $this->resultRedirectMock->expects($this->once())
             ->method('setPath')

app/code/Magento/Cms/Test/Unit/Controller/Adminhtml/Page/DeleteTest.php

@@ -124,10 +124,10 @@ public function testDeleteAction()
             ->method('delete');
 
         $this->messageManagerMock->expects($this->once())
-            ->method('addSuccess')
+            ->method('addSuccessMessage')
             ->with(__('The page has been deleted.'));
         $this->messageManagerMock->expects($this->never())
-            ->method('addError');
+            ->method('addErrorMessage');
 
         $this->eventManagerMock->expects($this->once())
             ->method('dispatch')
@@ -151,10 +151,10 @@ public function testDeleteActionNoId()
             ->willReturn(null);
 
         $this->messageManagerMock->expects($this->once())
-            ->method('addError')
+            ->method('addErrorMessage')
             ->with(__('We can\'t find a page to delete.'));
         $this->messageManagerMock->expects($this->never())
-            ->method('addSuccess');
+            ->method('addSuccessMessage');
 
         $this->resultRedirectMock->expects($this->once())
             ->method('setPath')
@@ -195,10 +195,10 @@ public function testDeleteActionThrowsException()
             );
 
         $this->messageManagerMock->expects($this->once())
-            ->method('addError')
+            ->method('addErrorMessage')
             ->with($errorMsg);
         $this->messageManagerMock->expects($this->never())
-            ->method('addSuccess');
+            ->method('addSuccessMessage');
 
         $this->resultRedirectMock->expects($this->once())
             ->method('setPath')

app/code/Magento/Cms/Test/Unit/Controller/Adminhtml/Page/EditTest.php

@@ -139,7 +139,7 @@ public function testEditActionPageNoExists()
             ->willReturn(null);
 
         $this->messageManagerMock->expects($this->once())
-            ->method('addError')
+            ->method('addErrorMessage')
             ->with(__('This page no longer exists.'));
 
         $this->resultRedirectFactoryMock->expects($this->atLeastOnce())

app/code/Magento/Cms/Test/Unit/Controller/Adminhtml/Page/MassDeleteTest.php

@@ -68,9 +68,9 @@ public function testMassDeleteAction()
             ->willReturn(new \ArrayIterator($collection));
 
         $this->messageManagerMock->expects($this->once())
-            ->method('addSuccess')
+            ->method('addSuccessMessage')
             ->with(__('A total of %1 record(s) have been deleted.', $deletedPagesCount));
-        $this->messageManagerMock->expects($this->never())->method('addError');
+        $this->messageManagerMock->expects($this->never())->method('addErrorMessage');
 
         $this->resultRedirectMock->expects($this->once())
             ->method('setPath')

app/code/Magento/Cms/Test/Unit/Controller/Adminhtml/Page/MassDisableTest.php

@@ -67,9 +67,9 @@ public function testMassDisableAction()
             ->willReturn(new \ArrayIterator($collection));
 
         $this->messageManagerMock->expects($this->once())
-            ->method('addSuccess')
+            ->method('addSuccessMessage')
             ->with(__('A total of %1 record(s) have been disabled.', $disabledPagesCount));
-        $this->messageManagerMock->expects($this->never())->method('addError');
+        $this->messageManagerMock->expects($this->never())->method('addErrorMessage');
 
         $this->resultRedirectMock->expects($this->once())
             ->method('setPath')

app/code/Magento/Cms/Test/Unit/Controller/Adminhtml/Page/MassEnableTest.php

@@ -67,9 +67,9 @@ public function testMassEnableAction()
             ->willReturn(new \ArrayIterator($collection));
 
         $this->messageManagerMock->expects($this->once())
-            ->method('addSuccess')
+            ->method('addSuccessMessage')
             ->with(__('A total of %1 record(s) have been enabled.', $enabledPagesCount));
-        $this->messageManagerMock->expects($this->never())->method('addError');
+        $this->messageManagerMock->expects($this->never())->method('addErrorMessage');
 
         $this->resultRedirectMock->expects($this->once())
             ->method('setPath')

app/code/Magento/Cms/Test/Unit/Controller/Page/PostDataProcessorTest.php

@@ -65,7 +65,7 @@ public function testValidateRequireEntry()
             'title' => ''
         ];
         $this->messageManagerMock->expects($this->once())
-            ->method('addError')
+            ->method('addErrorMessage')
             ->with(__('To apply changes you should fill in hidden required "%1" field', 'Page Title'));
 
         $this->assertFalse($this->postDataProcessor->validateRequireEntry($postData));