PIP runner introduction

[richtja]

This PR introduces a new dependency runner called pip. With this runner, avocado will be able to manipulate with python packages in test environment based on the test dependency configuration. The runner will install pip into the test environment, and then it can call pip install or pip uninstall commands. For example, this feature can be used for running coverage.py inside different environments than process.

[codecov]

Codecov Report

Attention: Patch coverage is 80.00000% with 9 lines in your changes missing coverage. Please review.

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Files with missing lines	Patch %	Lines
avocado/plugins/runners/pip.py	80.00%	9 Missing ⚠️

Additional details and impacted files

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[clebergnu]

Hi @richtja ,

This is a great idea, and a have a few comments for immediate changes, and somethings that can/should follow up later.

As for immediate changes, I mentioed the req-pac bits in the selftests.

Also, please add this variant to the nrunner-interface suite in selftests/check.py. While at it, add a selftests/functional/nrunner_interface.py.data/recipe_runnable_pip.json file (which can be a link or copy of the existing example file in this PR), but consider its actual execution and network access, etc.

It'd also be nice to add a test with a dependency as an example. I found that it's possible to do something like examples/tests/dependency_pip.py:

from avocado import Test, fail_on


class Pip(Test):
    """
    :avocado: dependency={"type": "pip", "name": "pip", "action": "install"}
    """

    @fail_on(ImportError)
    def test(self):
        import pip

It may seem pointless, but it's something that can run pretty much in every Python environment without causing disruption (installing extra modules).

As future points:

1. This looks like it could be part of a replacement for the use of eggs for Avocado's own automatic deployment
2. It would be nice to support the location destination where the pip modules will be installed (such as a venv). This would be especially useful for Avocado's own automatic deployment.
3. Support for multiple pip packages instead of one at a time

[richtja]

Hi @clebergnu, thanks for your review. I have updated the PR based on your suggestions. Please have a look.