Requirements now depend on python version

[potiuk]

Generate a separate requirements.txt file for each Python Version we support.

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[potiuk]

IT turned out that requirements are slightly different for different versions of python (especially in 1.10) so I had to add different version of requirements. At the same time I removed -pinned version. It's not really needed we should be able to easily install airflow now with one command:

  pip install apache-airflow[gcp]==1.10.10 \
      --constraint https://raw.githubusercontent.com/apache/airflow/1.10.10/requirements/requirements-python3.7.txt

[potiuk]

BTW. I am going to re-write some parts of it. I came to the conclusion that generating requirements is too big of a hassle for pre-commits (especially that we need them in different versions) so I will do a separate breeze command (and script for those not using Breeze) so that whenever you modify setup.py and new requirements are needed you will be notified via CI rather than pre-commit. I think it's much less impact on the development workflow.

Bear with me :).

[potiuk]

@kaxil @ashb @turbaszek @mik-laj @dimberman -> We have much nicer version now. Requirement generation is now checked only as travis build (separately for each python version) rather than pre-commit and you can esily manually generate the requirements with breeze (examples in doc). Also when you modify setup.py in the way that it will require regeneration of the reuqirements, the build in CI will fail, show you with nice, coloured diff what is added and will ask you to run breeze generate-requirements --python x.y as needed.

Pls review. That's the last thing to cherry-pick and test prod image in airflow 1.10.10

[codecov-io]

Codecov Report

Merging #7841 into master will decrease coverage by 22.37%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           master    #7841       +/-   ##
===========================================
- Coverage    87.1%   64.72%   -22.38%     
===========================================
  Files         928      927        -1     
  Lines       45025    44966       -59     
===========================================
- Hits        39217    29104    -10113     
- Misses       5808    15862    +10054

Impacted Files	Coverage Δ
...low/contrib/operators/wasb_delete_blob_operator.py	0% <0%> (-100%)	⬇️
airflow/contrib/hooks/vertica_hook.py	0% <0%> (-100%)	⬇️
airflow/contrib/sensors/__init__.py	0% <0%> (-100%)	⬇️
airflow/hooks/mssql_hook.py	0% <0%> (-100%)	⬇️
...viders/docker/example_dags/example_docker_swarm.py	0% <0%> (-100%)	⬇️
airflow/hooks/webhdfs_hook.py	0% <0%> (-100%)	⬇️
airflow/contrib/sensors/emr_base_sensor.py	0% <0%> (-100%)	⬇️
...irflow/contrib/operators/slack_webhook_operator.py	0% <0%> (-100%)	⬇️
...providers/google/cloud/example_dags/example_dlp.py	0% <0%> (-100%)	⬇️
...cncf/kubernetes/example_dags/example_kubernetes.py	0% <0%> (-100%)	⬇️
... and 501 more

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[potiuk]

OK. fixed separate requirements for different python versions is green in CI @kaxil @mik-laj -> do you want to take a look before I merge (@turbaszek ) ?