[AIRFLOW-3619] Improve flake8 excludes without excluding requirements.

[holdenk]

Jira

• [ X ] My PR addresses the following Airflow Jira issues and references them in the PR title. For example, "[AIRFLOW-XXX] My Airflow PR"
  • https://issues.apache.org/jira/browse/AIRFLOW-XXX
  • In case you are fixing a typo in the documentation you can prepend your commit with [AIRFLOW-XXX], code changes always need a Jira issue.

Description

• [ X ] Here are some details about my PR, including screenshots of any UI changes:

Update the flake8 excludes

Tests

• [ X ] My PR adds the following unit tests OR does not need testing for this extremely good reason:

We can verify the flake8 excludes with these three CI results:

1. Create new flake8 excludes (pass CI) - https://travis-ci.org/holdenk/incubator-airflow/builds/493380756
2. Create a style violation (fail CI in branch) - https://travis-ci.org/holdenk/incubator-airflow/builds/493385836
3. Fix style violation (pass CI in branch) - https://travis-ci.org/holdenk/incubator-airflow/builds/493386468

Commits

• [ X ] My commits all reference Jira issues in their subject lines, and I have squashed multiple commits if they address the same issue. In addition, my commits follow the guidelines from "How to write a good git commit message":
  1. Subject is separated from body by a blank line
  2. Subject is limited to 50 characters (not including Jira issue reference)
  3. Subject does not end with a period
  4. Subject uses the imperative mood ("add", not "adding")
  5. Body wraps at 72 characters
  6. Body explains "what" and "why", not "how"

There's 3 commits so it's clear the passing/failing of CI status

Documentation

• [ X ] In case of new functionality, my PR adds documentation that describes how to use it.
  • When adding new operators/hooks/sensors, the autoclass documentation generation needs to be added.
  • All the public functions and the classes in the PR contain docstrings that explain what it does

No change in usage required

Code Quality

• Passes flake8

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.