MC-31594: Duplicate SKU in the backend while importing products via CSV

Author: yelahin-serhiy

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

@@ -365,5 +365,7 @@ public function init($context)
         foreach ($this->validators as $validator) {
             $validator->init($context);
         }
+
+        return $this;
     }
 }