API: bump minimum Python to match SPEC0

Author: tacaswell

.github/workflows/testing.yml

@@ -12,7 +12,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: ['3.9', '3.10', '3.11', '3.12']
+        python-version: ['3.11', '3.12', '3.11']
       fail-fast: false
     steps:
 

setup.py

@@ -7,7 +7,7 @@
 # NOTE: This file must remain Python 2 compatible for the foreseeable future,
 # to ensure that we error out properly for people with outdated setuptools
 # and/or pip.
-min_version = (3, 7)
+min_version = (3, 11)
 if sys.version_info < min_version:
     error = """
 mpl-gui does not support Python {0}.{1}.