chore: Updates for Python 3.12 in CI (#1107)

- Drop support for Python 3.7 & 3.8 in CI.
- Use setuptools_scm recommended version file.

Update the approach to determine the current version of Pywr
to use the method recommended by setuptools_scm. This removes
the need for pkg_resources to be installed at runtime (which
is no longer installed by default in Python 3.12).

.github/workflows/build.yml

@@ -8,7 +8,7 @@ env:
   CIBW_TEST_COMMAND_LINUX: "{project}/.github/workflows/run-tests.sh {project}"
   CIBW_TEST_COMMAND_WINDOWS: "{project}\\.github\\workflows\\run-tests-windows.bat {project}"
   # Only build on Python 3.7+
-  CIBW_BUILD: cp37-* cp38-* cp39-* cp310-* cp311-*
+  CIBW_BUILD: cp39-* cp310-* cp311-* cp312-*
   # Skip 32-bit builds and MUSL Linux builds
   # MUSL Linux can be re-enabled more easily when updating from manylinux2014
   CIBW_SKIP: "*-win32 *-manylinux_i686 *-musllinux*"

pyproject.toml

@@ -1,9 +1,9 @@
 [build-system]
-requires = ["setuptools>=42", "wheel", "setuptools_scm[toml]>=3.4", "cython>=3", "numpy"]
+requires = ["setuptools>=62", "wheel", "setuptools_scm[toml]>=8.0", "cython>=3", "numpy"]
 
 # enable version inference
 [tool.setuptools_scm]
-
+version_file = "pywr/_version.py"
 
 [tool.black]
 line-length = 88

pywr/__init__.py

@@ -1,13 +1,13 @@
 #!/usr/bin/env python
 import os
 import sys
-from pkg_resources import get_distribution, DistributionNotFound
 
 try:
-    __version__ = get_distribution(__name__).version
-except DistributionNotFound:
-    # package is not installed
-    pass
+    from ._version import version as __version__
+    from ._version import version_tuple
+except ImportError:
+    __version__ = "unknown version"
+    version_tuple = (0, 0, "unknown version")
 
 if sys.platform == "win32":
     dll_folder = os.path.abspath(os.path.join(os.path.dirname(__file__), ".libs"))

setup.py

@@ -49,7 +49,12 @@ def finalize_options(self):
         author="Joshua Arnott",
         author_email="josh@snorfalorpagus.net",
         url="https://github.com/pywr/pywr",
-        setup_requires=["setuptools>=18.0", "setuptools_scm", "cython>=3", "numpy"],
+        setup_requires=[
+            "setuptools>=62",
+            "setuptools_scm[toml]>=8.0",
+            "cython>=3",
+            "numpy",
+        ],
         install_requires=[
             "pandas",
             "networkx",