greg.tests: migrate to pytest test runner

Migrates tests to use pytest as the test runner, replacing the standard library unittest framework.

Through its powerful fixture modelling approach, pytest allows us to compose test data according to the needs of individual tests. Without polluting the global namespace or requiring the database to be restructured/repopulated between each test, we are able to repurpose and compose test data in interesting ways.

added 2 commits

• 45834d3d - build: allow inner scopes to redefined outer names
• 50d55154 - build: disable duplicate code check

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changed title from greg.tests: migrate to purest test runner to greg.tests: migrate to pytest test runner

mentioned in merge request !10 (merged)

merged

mentioned in commit 34059d97