[AIRFLOW-2391] Fix to Flask 0.12.2

[Fokko]

Flask 0.12.3 has issues with Airflow and needs to be fixed. Therefore lock the version to 0.12.2 so the master is green again: http://flask.pocoo.org/docs/0.12/changelog/

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-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

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

Tests

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

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 #3277 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #3277   +/-   ##
=======================================
  Coverage   75.78%   75.78%           
=======================================
  Files         197      197           
  Lines       14699    14699           
=======================================
  Hits        11140    11140           
  Misses       3559     3559

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[jornh]

Apparently due to a packaging mishap with Flask 0.12.3. According to pallets/flask#2728 (comment) a fixed 0.12.4 should come out soon.

Sadly, until that happens it also leaves https://dist.apache.org/repos/dist/dev/incubator/airflow/1.10.0beta1/ in a state where you need to manually pin Flask to 0.12.2 as in e1bfb68.

I'll point to this warning from the dev mailing list as well - to maybe save the trouble for someone else.

@Fokko thank you for applying the fix so fast to both master and v1-10-test. It saved me a few cycles!

[Fokko]

Thanks @jornh for the background information. Really appreciate it. Are there any specific from Flask 1.12.{3,4} features that you want to be in there?

For now pinning it onto the specific version is the best solution. We had some issues with upgrades of dependencies that broke the Airflow install earlier.

[davidism]

I released 0.12.4 to fix this.

[Fokko]

I've reverted the pinned version: e561ea6 0ff434a

I've did some tests and it looks fine again, thanks @davidism for the quick fix!