import_export: better error message if upload failed

include/functions2.php

@@ -2449,4 +2449,20 @@
 
 		return $tmp;
 	}
+
+	function get_upload_error_message($code) {
+
+		$errors = array(
+			0 => __('There is no error, the file uploaded with success'),
+			1 => __('The uploaded file exceeds the upload_max_filesize directive in php.ini'),
+			2 => __('The uploaded file exceeds the MAX_FILE_SIZE directive that was specified in the HTML form'),
+			3 => __('The uploaded file was only partially uploaded'),
+			4 => __('No file was uploaded'),
+			6 => __('Missing a temporary folder'),
+			7 => __('Failed to write file to disk.'),
+			8 => __('A PHP extension stopped the file upload.'),
+		);
+
+		return $errors[$code];
+	}
 ?>