bpo-31583: Fix 2to3 for using with --add-suffix option (GH-3758)

bpo-31583: Fix 2to3 for using with --add-suffix option (GH-3758) · python/cpython@e3a523a

Original file line number	Diff line number	Diff line change
`@@ -80,7 +80,7 @@ def write_file(self, new_text, filename, old_text, encoding):`
`80`	`80`	`filename += self._append_suffix`
`81`	`81`	`if orig_filename != filename:`
`82`	`82`	`output_dir = os.path.dirname(filename)`
`83`		`-if not os.path.isdir(output_dir):`
	`83`	`+if not os.path.isdir(output_dir) and output_dir:`
`84`	`84`	`os.makedirs(output_dir)`
`85`	`85`	`self.log_message('Writing converted %s to %s.', orig_filename,`
`86`	`86`	`filename)`