Code linting on build

[kopf-archiver[bot]]

An issue by nolar at 2019-04-26 09:59:58+00:00 Original URL: https://github.com/zalando-incubator/kopf/issues/47  

Code should be automatically linted on every push, as part of the building process.

The coding guidelines should be some defaults of pylint, flake8, or both. One exception:

• Line length is 100 chars.

No linting scripts, no CLI options, just the standard CLI tool should already take all this into account — i.e. auto-detectable configs of these tools should be used (same as by the IDE).

[sergeyshevch]

Hi! I have a small PR related to this issue. I've added flake8 linter and fixed all related errors. But I was used 120 as a max line length.