feat!: drop Python 3.8 support

Python 3.8 reached end-of-life on 2024-10-07. Dependencies are now
actively dropping it — Dependabot PR #62 surfaced the first concrete
instance (virtualenv 21.5+ requires Python 3.9+, breaking the py38
CI job). Same rationale that drove dropping Python 3.7 in #32
applies more strongly here.

- setup.py: drop the 3.8 classifier; bump python_requires to >=3.9
- pyproject.toml: bump black target-version to py39
- tox.ini: drop py38 env and basepython entry
- README.rst: bump quick-start to Python 3.9-3.14
- .github/workflows/github-actions.yml: drop py38 (ubuntu) matrix
  entry (the only py38 job left after the multi-OS drop in #60)
- CHANGELOG.rst: add Unreleased section covering this PR, #60, #56,
  and #58

Branch protection on main was updated in lockstep — required
contexts dropped from 13 to 12.

BREAKING CHANGE: Edify now requires Python 3.9 or newer.

Closes #63

1 files changed, 1 insertions, 2 deletions

diff --git a/setup.py b/setup.py
index 22a3729..9547444 100755
--- a/setup.py
+++ b/setup.py
@@ -46,7 +46,6 @@ setup(
         'Programming Language :: Python',
         'Programming Language :: Python :: 3',
         'Programming Language :: Python :: 3 :: Only',
-        'Programming Language :: Python :: 3.8',
         'Programming Language :: Python :: 3.9',
         'Programming Language :: Python :: 3.10',
         'Programming Language :: Python :: 3.11',
@@ -69,7 +68,7 @@ setup(
     keywords=[
         # eg: 'keyword1', 'keyword2', 'keyword3',
     ],
-    python_requires='>=3.8',
+    python_requires='>=3.9',
     install_requires=[
         # eg: 'aspectlib==1.1.1', 'six>=1.7',
     ],