Hack: support setuptools < 77 with modern licenses (#4931)

Author: gpotter2

pyproject.toml

@@ -15,7 +15,7 @@ maintainers = [
     { name="Guillaume VALADON" },
     { name="Nils WEISS" },
 ]
-license = { text="GPL-2.0-only" }
+license = "GPL-2.0-only"
 requires-python = ">=3.7, <4"
 description = "Scapy: interactive packet manipulation tool"
 keywords = [ "network" ]
@@ -27,7 +27,6 @@ classifiers = [
     "Intended Audience :: Science/Research",
     "Intended Audience :: System Administrators",
     "Intended Audience :: Telecommunications Industry",
-    "License :: OSI Approved :: GNU General Public License v2 (GPLv2)",
     "Programming Language :: Python :: 3",
     "Programming Language :: Python :: 3 :: Only",
     "Programming Language :: Python :: 3.7",

setup.py

@@ -12,6 +12,7 @@
     raise OSError("Scapy no longer supports Python 2 ! Please use Scapy 2.5.0")
 
 try:
+    import setuptools
     from setuptools import setup
     from setuptools.command.sdist import sdist
     from setuptools.command.build_py import build_py
@@ -81,6 +82,31 @@ def build_package_data(self):
         # ensure there's a scapy/VERSION file
         _build_version(self.build_lib)
 
+
+# Patch so that for setuptools < 77 understands the 'license' version required
+# by modern setuptools. See https://github.com/secdev/scapy/issues/4849.
+# This allow us to keep support for Python 3.7
+try:
+    major = int(setuptools.__version__.split(".")[0])
+    if major < 77:
+        # We replace setuptools.dist.pyprojecttoml.apply_configuration with goo
+        from setuptools.config.pyprojecttoml import read_configuration, _apply
+
+        def _patched_apply_configuration(dist, filepath, *_):
+            # 1. We force ignore option errors regarding 'license'
+            config = read_configuration(filepath, True, ignore_option_errors=True, dist=dist)
+
+            # 2. We replace the license with the one it expected
+            if isinstance(config["project"]["license"], str):
+                config["project"]["license"] = {'text': config["project"]["license"]}
+
+            return _apply(dist, config, filepath)
+
+        setuptools.dist.pyprojecttoml.apply_configuration = _patched_apply_configuration
+except Exception:
+    pass
+
+
 setup(
     cmdclass={'sdist': SDist, 'build_py': BuildPy},
     data_files=[('share/man/man1', ["doc/scapy.1"])],