Replace pkg_resources with packaging

setuptools 82.0.0 removed pkg_resources, breaking the build.
Use packaging.requirements.Requirement instead, and switch the
Cython dependency string to PEP 508 format (no parentheses).

Author: ddelange

pyproject.toml

@@ -62,7 +62,7 @@ docs = [
 [build-system]
 requires = [
     "setuptools>=77.0.3",
-    "Cython(>=3.2.1,<4.0.0)"
+    "Cython>=3.2.1,<4.0.0"
 ]
 build-backend = "setuptools.build_meta"
 

setup.py

@@ -25,7 +25,7 @@
 from setuptools.command import build_ext as setuptools_build_ext
 
 
-CYTHON_DEPENDENCY = 'Cython(>=3.2.1,<4.0.0)'
+CYTHON_DEPENDENCY = 'Cython>=3.2.1,<4.0.0'
 
 CFLAGS = ['-O2']
 LDFLAGS = []
@@ -186,7 +186,8 @@ def finalize_options(self):
                         need_cythonize = True
 
         if need_cythonize:
-            import pkg_resources
+            # 'packaging' gets installed by 'wheel'
+            from packaging.requirements import Requirement
 
             # Double check Cython presence in case setup_requires
             # didn't go into effect (most likely because someone
@@ -199,8 +200,8 @@ def finalize_options(self):
                     'please install {} to compile asyncpg from source'.format(
                         CYTHON_DEPENDENCY))
 
-            cython_dep = pkg_resources.Requirement.parse(CYTHON_DEPENDENCY)
-            if Cython.__version__ not in cython_dep:
+            cython_dep = Requirement(CYTHON_DEPENDENCY)
+            if Cython.__version__ not in cython_dep.specifier:
                 raise RuntimeError(
                     'asyncpg requires {}, got Cython=={}'.format(
                         CYTHON_DEPENDENCY, Cython.__version__