Drop support for Python 3.10 (around January/April 2027)

Python 3.10 is expected to reach its end-of-life phase in October 2026 (PEP 619). We will remove support in two steps, approximately three and six months after it reached EOL.

How to remove support

Expected January 2027

• Update the version in README.md.
• Update various fields in pyproject.toml.
• Remove 3.10 from CI and test scripts.
• Update stubtest allow lists. Also check whether items can be moved to the common allow lists.
• Remove requires-python >= 3.11 and python-version >= 3.11 from METADATA.toml.
• Remove the version suffix from regression tests ending with -py311.py.
• Remove tomli from requirements-tests.txt.

Expected April 2027

• Remove 3.10 exclusive branches from stubs.
  • Switch EnumType/EnumMeta names in stdlib/enum.pyi, making EnumType the "real" name
• Remove obsolete stdlib modules (see VERSIONS).
  • binhex
  • distutils.command.bdist_msi
• Replace typing_extensions imports.
  • TypeVarTuple
  • Required/NotRequired
  • Self
  • LiteralString
  • dataclass_transform
• Update "Supported type system features" section in CONTRIBUTING.md as necessary.

(Please amend as necessary.)

Start with the January 2027 checklist in README.md, pyproject.toml, CI and test scripts, stubtest allow lists, METADATA.toml, regression tests, and requirements-tests.txt. Then review the April checklist in stdlib/enum.pyi, VERSIONS, the affected stubs, and CONTRIBUTING.md. Done means Python 3.10 support is removed across both stages and the relevant tests and metadata are updated.