fix #918: use packaging from setuptools for self-build

Author: RonnyPfannschmidt

CHANGELOG.rst

@@ -3,6 +3,7 @@ v8.0.2
 
 bugfix
 ------
+* fix #918: use packaging from setuptools for self-build
 * fix #914: ignore the deprecated git archival plugin as its integrated now
 * fix #912: ensure mypy safety of the version template + regression test
 * fix #913: use 240s timeout instead of 20 for git unshallow

pyproject.toml

@@ -4,7 +4,6 @@
 build-backend = "_own_version_helper"
 requires = [
   'importlib-metadata>=4.6; python_version < "3.10"',
-  "packaging>=20",
   "rich",
   "setuptools>=61",
   'tomli; python_version < "3.11"',

src/setuptools_scm/_version_cls.py

@@ -5,8 +5,12 @@
 from typing import Type
 from typing import Union
 
-from packaging.version import InvalidVersion
-from packaging.version import Version as Version
+try:
+    from packaging.version import InvalidVersion
+    from packaging.version import Version as Version
+except ImportError:
+    from setuptools.extern.packaging.version import InvalidVersion  # type: ignore
+    from setuptools.extern.packaging.version import Version as Version  # type: ignore
 
 
 class NonNormalizedVersion(Version):