feat!: Drop support for Python 3.8 (eol 2024-10-07)

[devin-ai-integration]

feat!: Drop support for Python 3.8 (eol 2024-10-07)

Summary

This PR removes support for Python 3.8 (which reached end-of-life on October 7, 2024) and adds support for Python 3.13. The changes include updating package classifiers, CI workflows, and upgrading Sphinx to resolve Python 3.13 compatibility issues.

Key Changes:

• ✅ Remove Python 3.8 support, bump minimum to Python 3.9
• ✅ Add Python 3.13 support and testing
• ✅ Update GitHub Actions workflows to test Python 3.9-3.13
• ✅ Upgrade Sphinx from ^1.3.0 to ^7.0.0 for Python 3.13 compatibility
• ✅ Update mypy configuration to use Python 3.9 as base version

Breaking Change: This is a breaking change as it drops support for Python 3.8. The Release-As version should reflect this as a major version bump.

Review & Testing Checklist for Human

• Test library functionality with Python 3.9-3.12 to ensure no regressions were introduced during the upgrade
• Verify documentation builds correctly with the new Sphinx 7.x version and that the generated docs look as expected
• Test actual Python 3.13 compatibility beyond CI checks - try importing and using the library with Python 3.13
• Confirm Release-As version strategy is appropriate for this breaking change (should be major version bump)
• Validate that Sphinx 7.x upgrade doesn't introduce any documentation rendering issues or theme compatibility problems

Recommended Test Plan:

1. Install the library in fresh Python 3.9, 3.11, 3.12, and 3.13 environments
2. Run the test suite in each environment
3. Build and review the documentation locally
4. Test basic SSE client functionality to ensure core features work

---

Diagram

flowchart TD
    A[pyproject.toml]:::major-edit --> B[Python Version Classifiers]
    A --> C[Sphinx Dependencies]
    A --> D[MyPy Configuration]
    
    E[GitHub Actions CI]:::major-edit --> F[Python Test Matrix]
    E --> G[Documentation Build]
    
    H[README.md]:::minor-edit --> I[Python Version Requirements]
    
    J[Library Code]:::context --> K[SSE Client Functionality]
    J --> L[Event Source Implementation]
    
    subgraph Legend
        L1[Major Edit]:::major-edit
        L2[Minor Edit]:::minor-edit  
        L3[Context/No Edit]:::context
    end
    
    classDef major-edit fill:#90EE90
    classDef minor-edit fill:#ADD8E6
    classDef context fill:#FFFFFF

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Notes

• The Sphinx upgrade from 1.3.0 to 7.0.0 was necessary to resolve Python 3.13 compatibility issues where the pipes and imghdr modules were removed
• All CI checks are passing across Python 3.9-3.13 on both Linux and Windows
• This change aligns with the Python 3.8 end-of-life date and follows the same pattern applied across other LaunchDarkly Python repositories
• The documentation build was verified locally with Python 3.13 and Sphinx 7.3.7

Link to Devin run: https://app.devin.ai/sessions/3f70248c29dd4d5eb70be4a05a78ce3a

Requested by: @keelerm84

[devin-ai-integration]

Original prompt from mkeeler@launchdarkly.com:

SYSTEM:
=== BEGIN THREAD HISTORY (in #sdks-python) ===
GitHub (U01V5FFUQ1E): 

[launchdarkly/python-server-sdk] Pull request merged by keelerm84

Matthew Keeler (U02FZSQUVCL): <@U0915543DJ7> if you look at sha 02076650064d8a20f792c80cda3249a7aa7e336a from the python-server-sdk repository, you will see a commit where I've dropped python 3.8 support from one of our libraries. I also increased testing support up to 3.13.

I need you to make the same type of changes across multiple different repositories:

• <https://github.com/launchdarkly/python-server-sdk-otel>
• <https://github.com/launchdarkly/python-server-sdk-ai>
• <https://github.com/launchdarkly/python-eventsource>
• <https://github.com/launchdarkly/openfeature-python-server>
• <https://github.com/launchdarkly/hello-python>
• <https://github.com/launchdarkly/hello-openfeature-python-server>
For each of these repositories we want to make sure that:

1. We bump the minimum to 3.9.
2. Update the README to reflect this new minimum.
3. Update all github action files to no longer include 3.8.
4. Anywhere we list the versions of python that are supported, we should make sure to expand to include 3.13.
When working on the repositories, you should work under a branch named: mk/sdk-1351/3.8

The PR title should be similar to what you saw in the provided SHA. The commit body should also include a "Release-As: X.Y.Z" designation. That release number should be the next non-breaking version number. For example, if the last tag was 1.2.3, then this should be "Release-As: 1.3.0". Or if it's "0.3.0", it should be "Release-As: 0.4.0".

Matthew Keeler (U02FZSQUVCL): <@U0915543DJ7> see my last message and do that please.

Cursor (U0915543DJ7): <@U02FZSQUVCL> deleted "Update Python support across repositories"

<@U02FZSQUVCL> deleted "Update Python support across repositories"

Matthew Keeler (U02FZSQUVCL): <@U0915543DJ7> help

Cursor (U0915543DJ7): Welcome to Cursor for Slack! Here's how to use it:

Welcome! Here's how to use Cursor in Slack:


*Start an Agent*

Create a new agent to work on your task
```@Cursor [your task description]```

_Example:_ `@Cursor Fix the login bug we discussed in this thread`

:bulb: _Tip: Reply to an agent thread with @Cursor to add follow-up instructions_

*Agent Settings*

View and edit your default model, repository, and branch
```@Cursor settings```

Use a different model, repository, or branch for a single agent
```@Cursor [branch=dev, model=o3, repo=torvalds/linux] Fix the login bug```

*More Commands*


_Cursor agents run in the background and notify you when complete_

Matthew Keeler (U02FZSQUVCL): <@U0915543DJ7> list agents

Cursor (U0915543DJ7): Your Cursor Agents:
• <https://cursor.com/background-agent?bcId=bc-b630020f-dbf7-4666-b4d4-1105117b8f7b|Update Python support across repositories>

_Last 24 hours_

Cursor (U0915543DJ7): Background agent has successfully finished!

Background agent has successfully finished!

*Repository:* `launchdarkly/gonfalon`
*Branch:* `cursor/update-python-support-across-repositories-569b`

Matthew Keeler (U02FZSQUVCL): @Devin I’m sorry. I tried another AI bot but nothing can replace you. :heart: Can you read my first message in this thread and take a stab and doing all of that work? Thanks love!
=== END THREAD HISTORY ===

The latest message is the one right above that tagged you.

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