Using flake8, I found some bugs in the standard libraries and tools.

I already fixed another flake8 error:
---
commit 28e61650b23119b68cd7943ccc01b8b9af1b4103
Author: Victor Stinner <victor.stinner@gmail.com>
Date:   Tue Nov 28 00:34:08 2017 +0100

    bpo-31245: asyncio: Fix typo, isistance => isinstance (#4594)
---

Attached patch fix 3 bugs found by the flake8 F841 warning.

Note: Python 2.7 is not impacted by the turtledemo bug, but it's impacted by the two other bugs.

New changeset 696b501cd11dc429a0f661adeb598bfaf89e4112 by Victor Stinner in branch 'master':
bpo-32155: Bugfixes found by flake8 F841 warnings (#4608)
https://github.com/python/cpython/commit/696b501cd11dc429a0f661adeb598bfaf89e4112

If you have replaced self.DEFAULT_REALM with realm why not replace self.DEFAULT_REPOSITORY with repository?

I don't know what is correct. Added distutils experts for review.

> If you have replaced self.DEFAULT_REALM with realm why not replace self.DEFAULT_REPOSITORY with repository?

Oh, I didn't notice that there is also a repository variable which is not used in all code paths.

> I don't know what is correct. Added distutils experts for review.

Now I'm not sure that my realm change is correct.

I don't think distutils changes are correct.

    ('realm', self.DEFAULT_REALM)

'realm' is the config name and 'self.DEFAULT_REALM' is its default value. In the 'for key, default in ...:' loop,

1. It checks if it's already set in the config file
2. Sets its value to 'current' if it does
3. If it doesn't, uses self.DEFAULT_REALM

distutils sets default values for undefined options via 'finalize_options' methods and there is the following command in 'PyPIRCCommand.finalize_options()' method:

    if self.realm is None:
        self.realm = self.DEFAULT_REALM

So unless there is a user set value for the 'realm' option (see the 'upload' and 'register' commands), 'self.realm' equals to 'self.DEFAULT_REALM'.

I'd remove the following code instead:

    realm = self.realm or self.DEFAULT_REALM

The best course of action would be to revert the distutils changes.

There are a handful of tickets related to register/upload commands, which are funky commands with their own config file not 100% in line with other distutils commands.  Changes in that code need tests.

I proposed PR 4618 to revert the distutils.config changes.

New changeset 6979fcdc91114b1ccb16345e26734d6df4cccbc3 by Victor Stinner in branch '3.6':
bpo-32155: Bugfixes found by flake8 F841 warnings (#4619)
https://github.com/python/cpython/commit/6979fcdc91114b1ccb16345e26734d6df4cccbc3

New changeset 71bd588646b282c9eebc390b31184a5bdb54e712 by Victor Stinner in branch 'master':
bpo-32155: Revert distutils.config change (#4618)
https://github.com/python/cpython/commit/71bd588646b282c9eebc390b31184a5bdb54e712

The main bugs have been fixed in Python 3.6 and 3.7 (master).

Python 2.7 only has the bug in Tools/scripts/treesync.py, but I don't think that it's worth it to fix this old script in the stable 2.7 branch. I just removed this script from the master branch (bpo-32159).