Preserve all context keys during serialization

[yannlambret]

When instantiating a PythonVirtualenvOperator, part of the context is propagated based on the requirements constructor parameter. The current logic implementation prevents 'pendulum' or 'apache-airflow' keys to be added to the Airflow context as soon as a version specifier is used.

For instance this requirement list will have the expected behavior:

        op = PythonVirtualenvOperator(
            task_id="task",
            python_callable=func,
            requirements=["pendulum"],
            system_site_packages=False,
        )

Whereas this one will cause the pendulum objects to be stripped out of the context:

        op = PythonVirtualenvOperator(
            task_id="task",
            python_callable=func,
            requirements=["pendulum<3.0"],
            system_site_packages=False,
        )

This PR aims to fix these limitations.

[boring-cyborg]

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[potiuk]

Nice one - however, maybe instead of regexp you should parse the requirement with packaging requirements and take name of distribution from there: https://packaging.pypa.io/en/stable/requirements.html

This has additional advantage of actually parsing the requirements and will fail early in case any of the requirements are not following the specification.

[yannlambret]

Hello @potiuk, thank you for the suggestion. I modified the code to use packaging.requirements. I did my best to implement a reasonably robust parsing logic, by taking care of a few edge cases (comments, etc.). Let me know what you think.

[potiuk]

Nice! One, very small nit. Good points with comment removals.

[boring-cyborg]

Awesome work, congrats on your first merged pull request! You are invited to check our Issue Tracker for additional contributions.

[amoghrajesh]

We do not account for the case when more than one are passed.