Bump setuptools required version because of setuptools_scm v8

Technically could work with older setuptools and setuptools_scm==7, but encoding that matrix of dependencies is not something I think is worth worrying about, and setuptools 64 is over a year old (though not by a _whole_ lot).

doc/api/next_api_changes/development/26849-KS.rst

@@ -0,0 +1,5 @@
+Minimum version of setuptools bumped to 64
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+To comply with requirements of ``setuptools_scm``, the minimum version of ``setuptools``
+has been increased from 42 to 64.

doc/devel/dependencies.rst

@@ -228,7 +228,7 @@ Setup dependencies
   runtime dependency.
 - `PyBind11 <https://pypi.org/project/pybind11/>`_ (>= 2.6). Used to connect C/C++ code
   with Python.
-- `setuptools <https://pypi.org/project/setuptools/>`_ (>= 42).
+- `setuptools <https://pypi.org/project/setuptools/>`_ (>= 64).
 - `setuptools_scm <https://pypi.org/project/setuptools-scm/>`_ (>= 7).  Used to
   update the reported ``mpl.__version__`` based on the current git commit.
   Also a runtime dependency for editable installs.

pyproject.toml

@@ -4,10 +4,17 @@ requires = [
     "certifi>=2020.06.20",
     "numpy>=1.25",
     "pybind11>=2.6",
-    "setuptools>=42",
+    "setuptools>=64",
     "setuptools_scm>=7",
 ]
 
+[tool.setuptools_scm]
+version_scheme = "release-branch-semver"
+local_scheme = "node-and-date"
+write_to = "lib/matplotlib/_version.py"
+parentdir_prefix_version = "matplotlib-"
+fallback_version = "0.0+UNKNOWN"
+
 [tool.isort]
 known_pydata = "numpy, matplotlib.pyplot"
 known_firstparty = "matplotlib,mpl_toolkits"

requirements/testing/mypy.txt

@@ -24,5 +24,6 @@ pillow>=8
 pyparsing>=2.3.1
 python-dateutil>=2.7
 setuptools_scm>=7
+setuptools>=64
 
 importlib-resources>=3.2.0 ; python_version < "3.10"

setup.py

@@ -340,7 +340,10 @@ def make_release_tree(self, base_dir, files):
         "python-dateutil>=2.7",
     ] + (
         # Installing from a git checkout that is not producing a wheel.
-        ["setuptools_scm>=7"] if (
+        # setuptools_scm warns with older setuptools, which turns into errors for our
+        # test suite. However setuptools_scm does not themselves pin the version of
+        # setuptools.
+        ["setuptools_scm>=7", "setuptools>=64"] if (
             Path(__file__).with_name(".git").exists() and
             os.environ.get("CIBUILDWHEEL", "0") != "1"
         ) else []