Rely on importlib_metadata for Python 3.9 and earlier. Fixes pypa#630.

Author: jaraco

pyproject.toml

@@ -36,7 +36,7 @@ dependencies = [
   "pyproject_hooks",
   # not actually a runtime dependency, only supplied as there is not "recommended dependency" support
   'colorama; os_name == "nt"',
-  'importlib-metadata >= 0.22; python_version < "3.8"',
+  'importlib-metadata >= 4.6; python_version < "3.10"',
   'tomli >= 1.1.0; python_version < "3.11"',
 ]
 

src/build/_importlib.py

@@ -1,7 +1,7 @@
 import sys
 
 
-if sys.version_info >= (3, 8):
+if sys.version_info >= (3, 10):
     from importlib import metadata
 else:
     import importlib_metadata as metadata