WIP: Obey HTTP status codes from upstream.

[gastonfournier]

Description

Previously we have treated any status code as equal. This PR changes that to allow 429 and 50x status codes to incrementally increase the interval between each time we call. And then gradually decrease once it starts succeeding.

This is a port of Unleash/unleash-java-sdk#221 into the Python SDK

Type of change

• New feature (non-breaking change which adds functionality)
• This change requires a documentation update

How Has This Been Tested?

Please describe the tests that you ran to verify your changes.

• Unit tests
• Spec Tests
• Integration tests / Manual Tests

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

[stale]

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[stale]

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.