bpo-38878: Fix os.PathLike __subclasshook__ (GH-17336)

Quick subclasshook fix using the same method is being used in collections.abc (up to a certain degree).
diff --git a/Lib/test/test_os.py b/Lib/test/test_os.py
index f44ddba..82c441c 100644
--- a/Lib/test/test_os.py
+++ b/Lib/test/test_os.py
@@ -4048,6 +4048,14 @@
         self.assertRaises(ZeroDivisionError, self.fspath,
                           FakePath(ZeroDivisionError()))
 
+    def test_pathlike_subclasshook(self):
+        # bpo-38878: subclasshook causes subclass checks
+        # true on abstract implementation.
+        class A(os.PathLike):
+            pass
+        self.assertFalse(issubclass(FakePath, A))
+        self.assertTrue(issubclass(FakePath, os.PathLike))
+
     def test_pathlike_class_getitem(self):
         self.assertIs(os.PathLike[bytes], os.PathLike)