Drop support for SCons 3.x

.github/workflows/main.yml

@@ -48,7 +48,7 @@ jobs:
         run: python3 -m pip install -U pip setuptools wheel
       - name: Install Python dependencies
         run: |
-          python3 -m pip install ruamel.yaml scons==3.1.2
+          python3 -m pip install ruamel.yaml scons==4.0.1
       - name: Build Cantera
         run: |
           python3 `which scons` build env_vars=all -j4 debug=n --debug=time \
@@ -104,7 +104,7 @@ jobs:
       run: python3 -m pip install -U pip setuptools wheel
     - name: Install Python dependencies
       run: |
-        python3 -m pip install ruamel.yaml scons==3.1.2 numpy${{ matrix.numpy }} \
+        python3 -m pip install ruamel.yaml scons==4.0.1 numpy${{ matrix.numpy }} \
           cython${{ matrix.cython }} pandas pytest \
           pytest-github-actions-annotate-failures pytest-xdist pint graphviz
     - name: Build Cantera

SConstruct

@@ -68,16 +68,6 @@ Additional command options:
 #                          screen instead of doing <command>, for example
 #                          'scons build dump'. For debugging purposes.
 
-# This f-string is deliberately here to trigger a SyntaxError when
-# SConstruct is parsed by Python 2. This seems to be the most robust
-# and simplest option that will reliably trigger an error in Python 2
-# and provide actionable feedback for users.
-f"""
-Cantera must be built using Python 3.10 or higher. You can invoke SCons by executing
-    python3 `which scons`
-followed by any desired options.
-"""
-
 from pathlib import Path
 import sys
 import os
@@ -100,7 +90,7 @@ from buildutils import (Option, PathOption, BoolOption, EnumOption, Configuratio
 
 # ensure that Python and SCons versions are sufficient for the build process
 EnsurePythonVersion(3, 7)
-EnsureSConsVersion(3, 0, 0)
+EnsureSConsVersion(4, 0, 0)
 
 if not COMMAND_LINE_TARGETS:
     # Print usage help
@@ -844,8 +834,6 @@ if os.name == "nt":
     elif windows_compiler_env["toolchain"] == "mingw":
         toolchain = ["mingw", "f90"]
         extraEnvArgs["F77"] = None
-        # Next line fixes https://github.com/SCons/scons/issues/2683
-        extraEnvArgs["WINDOWS_INSERT_DEF"] = 1
 
     elif windows_compiler_env["toolchain"] == "intel":
         toolchain = ["intelc"] # note: untested

doc/sphinx/develop/compiling/dependencies.md

@@ -40,7 +40,7 @@ compiler is required only if you plan to build the Fortran module.
 - SCons:
 
   - <http://scons.org/tag/releases.html>
-  - Works with versions >= 3.0.0
+  - Works with versions >= 4.0.0
   - On Windows, more recent SCons versions are required to support each new version of
     the MSVC compiler.