flake8 test fails with master as of 2018.09.07

[latricewilgus]

Please follow the guide below

• You will be asked some questions and requested to provide some information, please read them carefully and answer honestly
• Put an x into all the boxes [ ] relevant to your issue (like this: [x])
• Use the Preview tab to see what your issue will actually look like

---

Make sure you are using the latest version: run youtube-dl --version and ensure your version is 2018.09.01. If it's not, read this FAQ entry and update. Issues with outdated version will be rejected.

• I've verified and I assure that I'm running youtube-dl 2018.09.01

Before submitting an issue make sure you have:

• At least skimmed through the README, most notably the FAQ and BUGS sections
• Searched the bugtracker for similar issues including closed ones
• Checked that provided video/audio/playlist URLs (if any) are alive and playable in a browser

What is the purpose of your issue?

• Bug report (encountered problems with youtube-dl)
• Site support request (request for adding support for a new site)
• Feature request (request for a new functionality)
• Question
• Other

---

Hi

the flake8 test (run by make codetest/make test/...) fails with

./youtube_dl/extractor/seznamzpravy.py:168:17: F812 list comprehension redefines 'url' from line 156
./youtube_dl/extractor/motherless.py:172:21: F812 list comprehension redefines 'video_id' from line 161
./youtube_dl/extractor/generic.py:3115:51: F812 list comprehension redefines 'mobj' from line 2928
./youtube_dl/extractor/dtube.py:62:31: F841 local variable 'e' is assigned to but never used

Note that F812 is specific to python 2.7 according to flake8 documentation[0].

There are two possible ways to handle these:
a) rename the offending variables / remove the assignment
b) add '# noqa: F812', '# noqa: F841' to the offending lines.

Which way to go is a design decision and up to you (the maintainers, developers).

[0] http://flake8.pycqa.org/en/latest/user/error-codes.html