Add category to url_key error message

Error message for url_key is not wrong but too short
Use addFailedCategory() to add category to error message

Issue: 10697

Author: An Van den Bosch

app/code/Magento/CatalogImportExport/Model/Import/Product/CategoryProcessor.php

@@ -118,8 +118,12 @@ protected function createCategory($name, $parentId)
         $category->setIsActive(true);
         $category->setIncludeInMenu(true);
         $category->setAttributeSetId($category->getDefaultAttributeSetId());
-        $category->save();
-        $this->categoriesCache[$category->getId()] = $category;
+        try {
+            $category->save();
+            $this->categoriesCache[$category->getId()] = $category;
+        } catch (\Exception $e){
+            $this->addFailedCategory($category, $e);
+        }
 
         return $category->getId();
     }