[AIRFLOW-2687] Move unittest2 to devel in setup.py

[sekikn]

Make sure you have checked all steps below.

JIRA

• 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-2687
  • 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

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

This PR moves the package unittest2 from
devel_ci to devel in setup.py, since
the latter is the minimal required packages
for development and unittest2 is considered
as one of them.

Tests

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

No additional test, since it's a fix for library dependency, not for feature.
I ran pip install -U -e "[.devel]" locally, and confirmed that unittest2 is installed on Python2 and not on Python3.

Commits

• 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
  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"

Documentation

• 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.

Code Quality

• Passes git diff upstream/master -u -- "*.py" | flake8 --diff

[codecov-io]

Codecov Report

Merging #3555 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #3555   +/-   ##
=======================================
  Coverage   77.45%   77.45%           
=======================================
  Files         204      204           
  Lines       15299    15299           
=======================================
  Hits        11850    11850           
  Misses       3449     3449

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[Fokko]

Can't we change this to something that is both Python 2 and 3 compatible? Also not PY3 is less readable than PY2.

[sekikn]

Closing this since the same fix has already been merged as #3581.

[ron819]

@sekikn The jira ticket is still open

[sekikn]

@ron819 @ashb Thanks for notifying and closing ;)