Issue #15307: Skipped test_venv:test_prefixes when run from a venv.
diff --git a/Lib/test/test_venv.py b/Lib/test/test_venv.py
index c98a14e..6f73fcf 100644
--- a/Lib/test/test_venv.py
+++ b/Lib/test/test_venv.py
@@ -87,6 +87,8 @@
             print('    %r' % os.listdir(bd))
         self.assertTrue(os.path.exists(fn), 'File %r should exist.' % fn)
 
+    @unittest.skipIf(sys.prefix != sys.base_prefix, 'Test not appropriate '
+                     'in a venv')
     def test_prefixes(self):
         """
         Test that the prefix values are as expected.