Drop Python 3.9 support

[pankajastro]

Based on the discussion in PR #2117, we are officially dropping support for Python 3.9 from the main branch. Python 3.9 support will be removed starting with Cosmos v1.12.0.

[netlify]

✅ Deploy Preview for sunny-pastelito-5ecb04 canceled.

Name	Link
🔨 Latest commit	a8fc3ba
🔍 Latest deploy log	https://app.netlify.com/projects/sunny-pastelito-5ecb04/deploys/6915f56300baa900088043ab

[Copilot]

Pull Request Overview

This PR drops official support for Python 3.9 from Astronomer Cosmos, starting with version 1.12.0, by updating the minimum required Python version to 3.10 and modernizing the codebase to use Python 3.10+ syntax features.

Key Changes:

• Updated minimum Python version from 3.9 to 3.10 in package configuration
• Converted test files to use parenthesized context manager syntax (PEP 617) introduced in Python 3.10
• Updated documentation examples to reference Python 3.11 instead of 3.9

Reviewed Changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
pyproject.toml	Updated requires-python to >=3.10, removed Python 3.9 from classifiers, test matrix, and Black's target-version configuration
tests/test_io.py	Converted with statements to use parenthesized context manager syntax
tests/test_cache.py	Converted with statements to use parenthesized context manager syntax
tests/operators/test_watcher.py	Converted multiple with statements to use parenthesized context manager syntax
tests/operators/test_local.py	Converted with statements to use parenthesized context manager syntax
tests/operators/test_kubernetes.py	Converted with statements to use parenthesized context manager syntax
tests/dbt/test_runner.py	Converted with statements to use parenthesized context manager syntax
tests/_triggers/test_watcher.py	Converted multiple with statements to use parenthesized context manager syntax
cosmos/dbt/graph.py	Converted with statement to use parenthesized context manager syntax
docs/contributing.rst	Updated documentation examples from Python 3.9 to Python 3.11

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.81%. Comparing base (fa645d8) to head (a8fc3ba).
⚠️ Report is 5 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2118   +/-   ##
=======================================
  Coverage   97.81%   97.81%           
=======================================
  Files          92       92           
  Lines        5961     5961           
=======================================
  Hits         5831     5831           
  Misses        130      130           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[pankajkoti]

Is it possible to add a highlight in the Changelog for 1.12.0 that we're dropping support for Python 3.9?

[tatiana]

Thanks, @pankajastro ! I agree with @pankajkoti , if you could add this to the changelog, it would be great.

We already breaking changes section.