The failing test was added with d4c76d960b8b286b75c933780416ace9cda682fd


commit d4c76d960b8b286b75c933780416ace9cda682fd
Author: INADA Naoki <methane@users.noreply.github.com>
Date:   Mon Oct 1 21:10:37 2018 +0900

    bpo-30167: Add test for module.__cached__ is None (GH-7617)

diff --git a/Lib/test/test_site.py b/Lib/test/test_site.py
index dc59e5917c..33a8f1a44c 100644
--- a/Lib/test/test_site.py
+++ b/Lib/test/test_site.py
@@ -389,6 +389,17 @@ class ImportSideEffectTests(unittest.TestCase):
                             "expected absolute path, got {}"
                             .format(os__cached__.decode('ascii')))

+    def test_abs_paths_cached_None(self):
+        """Test for __cached__ is None.
+
+        Regarding to PEP 3147, __cached__ can be None.
+
+        See also: https://bugs.python.org/issue30167
+        """
+        sys.modules['test'].__cached__ = None
+        site.abs_paths()
+        self.assertIsNone(sys.modules['test'].__cached__)
+


# Latest master

➜  cpython git:(master) ./python.exe -m test.regrtest test_inspect test_site
Run tests sequentially
0:00:00 load avg: 1.75 [1/2] test_inspect
0:00:02 load avg: 1.75 [2/2] test_site
test test_site failed -- Traceback (most recent call last):
  File "/Users/karthikeyansingaravelan/stuff/python/cpython/Lib/test/test_site.py", line 400, in test_abs_paths_cached_None
    site.abs_paths()
  File "/Users/karthikeyansingaravelan/stuff/python/cpython/Lib/site.py", line 101, in abs_paths
    for m in set(sys.modules.values()):
TypeError: unhashable type: 'dict'

test_site failed

== Tests result: FAILURE ==

1 test OK.

1 test failed:
    test_site

Total duration: 2 sec 868 ms
Tests result: FAILURE


➜  cpython git:(master) git checkout d4c76d960b8b286b75c933780416ace9cda682fd~1 Lib/test/test_site.py
➜  cpython git:(master) ✗ ./python.exe -m test.regrtest test_inspect test_site
Run tests sequentially
0:00:00 load avg: 1.49 [1/2] test_inspect
0:00:02 load avg: 1.49 [2/2] test_site

== Tests result: SUCCESS ==

All 2 tests OK.

Total duration: 2 sec 848 ms
Tests result: SUCCESS

Adding INADA Naoki for thoughts.


Thanks