Add AWS EMR System tests

[xinbinhuang]

Add system tests for two EMR related example DAGs.

The credentials are provided from ~/.aws/ following as in boto3 configuration. I feel like I should add some docs somewhere to indicate how to provide credentials for the system test, but not sure where... Please let me know if you would like me to add the documentation somewhere.

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[mik-laj]

I feel like I should add some docs somewhere to indicate how to provide credentials for the system test, but not sure where...

We have documentation about credentials in system tests:
https://github.com/apache/airflow/blob/master/TESTING.rst#forwarding-authentication-from-the-host.
You can still add a small note in the docstring for the file: tests/providers/amazon/aws/operators/test_emr_system.py

The best solution is to add a marker that will skip the tests if the file with credentials is not available. If you try to run tests for GCP and you do not have credentials then you will see the message below:

========================================================================================= short test summary info ==========================================================================================
SKIPPED [1] /Users/kamilbregula/devel/google-airflow/airflow/tests/conftest.py:308: The test requires credential file /files/airflow-breeze-config/keys/gcp_life_sciences.json: <TestCaseFunction test_run_example_dag_function>
============================================================================================ 1 skipped in 1.06s ============================================================================================

[xinbinhuang]

I feel like I should add some docs somewhere to indicate how to provide credentials for the system test, but not sure where...

We have documentation about credentials in system tests:
https://github.com/apache/airflow/blob/master/TESTING.rst#forwarding-authentication-from-the-host.
You can still add a small note in the docstring for the file: tests/providers/amazon/aws/operators/test_emr_system.py

The best solution is to add a marker that will skip the tests if the file with credentials is not available. If you try to run tests for GCP and you do not have credentials then you will see the message below:

========================================================================================= short test summary info ==========================================================================================
SKIPPED [1] /Users/kamilbregula/devel/google-airflow/airflow/tests/conftest.py:308: The test requires credential file /files/airflow-breeze-config/keys/gcp_life_sciences.json: <TestCaseFunction test_run_example_dag_function>
============================================================================================ 1 skipped in 1.06s ============================================================================================

@mik-laj Thanks for the suggestion. I took a look at the marker you mention, it needs to copy the credentials in the files/breeze_config/keys folder. For AWS system test, I think we can defer the discussion on sourcing credentials later as right now, we are still trying to add more helpers functions for AWS system test (i.e. #8581). So for this PR, I think it will better to use the default credentials for now, and we can change it after we have standardized the workflow.

What do you think?

[mik-laj]

@xinbinhuang I agree. We don't need it now, but you asked how to make the documentation. The best documentation is an intuitive program that has user-friendly messages

[xinbinhuang]

cc @feluelle @mustafagok - Feel free to take a look :)

@feluelle I can rebase on your changes once your PR is merged into master

[feluelle]

Please add emr.rst docs in the howto section. Besides that LGTM.

And if you PR is merged first I can rebase onto your changes (aws_system_helpers.py) - that's not a problem - you don't have to wait for my PR to be merged :)

[feluelle]

@xinbinhuang you can rebase onto latest master. The amazon_system_helpers.py is there :)

[xinbinhuang]

@mustafagok @feluelle Sorry for the late update, I have been swamped by other things in the last two weeks. I update the PR with your suggestions. PTAL :)

[xinbinhuang]

@feluelle @mustafagok Thanks for reviewing and merging!

[potiuk]

Fantastics! Thanks @feluelle !