2to3 doesn't work if called for file in current directory with --add-suffix option.
	
$ /d/repos/cpython/python.bat /d/repos/cpython/Tools/scripts/2to3 -n -W --add-suffix=3 test2to3.py
Running Debug|x64 interpreter...
WARNING: --write-unchanged-files/-W implies -w.
RefactoringTool: Skipping optional fixer: buffer
RefactoringTool: Skipping optional fixer: idioms
RefactoringTool: Skipping optional fixer: set_literal
RefactoringTool: Skipping optional fixer: ws_comma
RefactoringTool: Refactored test2to3.py
--- test2to3.py (original)
+++ test2to3.py (refactored)

--some changes--

Traceback (most recent call last):
  File "D:/repos/cpython/Tools/scripts/2to3", line 5, in <module>
    sys.exit(main("lib2to3.fixes"))
  File "D:\repos\cpython\lib\lib2to3\main.py", line 259, in main
    options.processes)
  File "D:\repos\cpython\lib\lib2to3\refactor.py", line 687, in refactor
    items, write, doctests_only)
  File "D:\repos\cpython\lib\lib2to3\refactor.py", line 282, in refactor
    self.refactor_file(dir_or_file, write, doctests_only)
  File "D:\repos\cpython\lib\lib2to3\refactor.py", line 728, in refactor_file
    *args, **kwargs)
  File "D:\repos\cpython\lib\lib2to3\refactor.py", line 339, in refactor_file
    write=write, encoding=encoding)
  File "D:\repos\cpython\lib\lib2to3\refactor.py", line 505, in processed_file
    self.write_file(new_text, filename, old_text, encoding)
  File "D:\repos\cpython\lib\lib2to3\main.py", line 84, in write_file
    os.makedirs(output_dir)
  File "D:\repos\cpython\\lib\os.py", line 221, in makedirs
    mkdir(name, mode)
FileNotFoundError: [WinError 3] The system cannot find the path specified: ''


It works well if I use absolute path for target file or set -o:

$ /d/repos/cpython/python.bat /d/repos/cpython/Tools/scripts/2to3 -n -W --add-suffix=3 /d/MyPythonScripts/test2to3.py

$ /d/repos/cpython/python.bat /d/repos/cpython/Tools/scripts/2to3 -n -W --add-suffix=3 -o . test2to3.py

Issue also effects 3.5

3.5 is in security-fix-only mode, and we use versions to indicate which versions we plan to fix the bug in.

Gotcha, sorry about that. Active uses 3.5, so I guess I would take it up
with them?

On Oct 3, 2017 2:27 PM, "R. David Murray" <report@bugs.python.org> wrote:

>
> R. David Murray <rdmurray@bitdance.com> added the comment:
>
> 3.5 is in security-fix-only mode, and we use versions to indicate which
> versions we plan to fix the bug in.
>
> ----------
> nosy: +r.david.murray
> versions:  -Python 3.5
>
> _______________________________________
> Python tracker <report@bugs.python.org>
> <https://bugs.python.org/issue31583>
> _______________________________________
>

Yes, redistributors sometimes backport non-security fixes if they consider them important enough.

Note that I haven't evaluated the merits of this issue, and there is a related issue about how 2to3 finds its fixers that this may overlap with.

Inserting (with 12 spaces)

            if not output_dir:
                output_dir = "./"

at lines 83 and 84 works as a temporary workaround.  `StdoutRefactoringTool` is not receiving an `output_dir` from `option`, which seems to only be an issue when `--add-sufix` is used.

New changeset e3a523a0fa16aec880880928303bfcbd1fb74bc2 by Łukasz Langa (Denis Osipov) in branch 'master':
bpo-31583: Fix 2to3 for using with --add-suffix option (GH-3758)
https://github.com/python/cpython/commit/e3a523a0fa16aec880880928303bfcbd1fb74bc2

New changeset 67067d85eb1df8c52399f9fc74dc4c1a32ec86cd by Łukasz Langa (Miss Islington (bot)) in branch '3.7':
bpo-31583: Fix 2to3 for using with --add-suffix option (GH-3758) (#6528)
https://github.com/python/cpython/commit/67067d85eb1df8c52399f9fc74dc4c1a32ec86cd

New changeset 1957e7b76a1319995360492223a4dfe1cd5d105c by Łukasz Langa (Miss Islington (bot)) in branch '3.6':
bpo-31583: Fix 2to3 for using with --add-suffix option (GH-3758) (GH-6529)
https://github.com/python/cpython/commit/1957e7b76a1319995360492223a4dfe1cd5d105c