gh-132947: Apply changes from importlib_metadata 8.7 (#137885)

* Copied files from python/importlib_metadata@b67ac80c49.

Lib/test/test_importlib/metadata/test_main.py

@@ -1,8 +1,7 @@
-import re
-import pickle
-import unittest
 import importlib
-import importlib.metadata
+import pickle
+import re
+import unittest
 from test.support import os_helper
 
 try:
@@ -10,8 +9,6 @@
 except ImportError:
     from .stubs import fake_filesystem_unittest as ffs
 
-from . import fixtures
-from ._path import Symlink
 from importlib.metadata import (
     Distribution,
     EntryPoint,
@@ -24,6 +21,9 @@
     version,
 )
 
+from . import fixtures
+from ._path import Symlink
+
 
 class BasicTests(fixtures.DistInfoPkg, unittest.TestCase):
     version_pattern = r'\d+\.\d+(\.\d)?'
@@ -157,6 +157,16 @@ def test_valid_dists_preferred(self):
         dist = Distribution.from_name('foo')
         assert dist.version == "1.0"
 
+    def test_missing_metadata(self):
+        """
+        Dists with a missing metadata file should return None.
+
+        Ref python/importlib_metadata#493.
+        """
+        fixtures.build_files(self.make_pkg('foo-4.3', files={}), self.site_dir)
+        assert Distribution.from_name('foo').metadata is None
+        assert metadata('foo') is None
+
 
 class NonASCIITests(fixtures.OnSysPath, fixtures.SiteDir, unittest.TestCase):
     @staticmethod