MAGETWO-59743: Product deleted after import with Replace behavior

Author: Bohdan Korablov

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

@@ -2304,7 +2304,7 @@ public function validateRow(array $rowData, $rowNum)
 
         $sku = $rowData[self::COL_SKU];
 
-        if (isset($this->_oldSku[$sku])) {
+        if (isset($this->_oldSku[$sku]) && Import::BEHAVIOR_REPLACE !== $this->getBehavior()) {
             // can we get all necessary data from existent DB product?
             // check for supported type of existing product
             if (isset($this->_productTypeModels[$this->_oldSku[$sku]['type_id']])) {
@@ -2356,7 +2356,7 @@ public function validateRow(array $rowData, $rowNum)
             $rowAttributesValid = $productTypeValidator->isRowValid(
                 $rowData,
                 $rowNum,
-                !isset($this->_oldSku[$sku])
+                !(isset($this->_oldSku[$sku]) && Import::BEHAVIOR_REPLACE !== $this->getBehavior())
             );
             if (!$rowAttributesValid && self::SCOPE_DEFAULT == $rowScope) {
                 // mark SCOPE_DEFAULT row as invalid for future child rows if product not in DB already