Merge branch '2.1-develop' of https://github.com/magento/magento2ce into 2.1.13-PR-0.1

Author: Oleksandr Iegorov

app/code/Magento/Cms/Helper/Page.php

@@ -152,7 +152,7 @@ public function prepareResultPage(Action $action, $pageId = null)
         $resultPage = $this->resultPageFactory->create();
         $this->setLayoutType($inRange, $resultPage);
         $resultPage->addHandle('cms_page_view');
-        $resultPage->addPageLayoutHandles(['id' => $this->_page->getIdentifier()]);
+        $resultPage->addPageLayoutHandles(['id' => str_replace('/', '_', $this->_page->getIdentifier())]);
 
         $this->_eventManager->dispatch(
             'cms_page_render',