Add workaround for test_raises_cyclic_reference in Python 3.5.{0,1}

testing/python/raises.py

@@ -159,13 +159,19 @@ class TestRaises:
         """
         Ensure pytest.raises does not leave a reference cycle (#1965).
         """
-        import gc
 
         class T:
             def __call__(self):
+                # Early versions of Python 3.5 have some bug causing the
+                # __call__ frame to still refer to t even after everything
+                # is done. This makes the test pass for them.
+                if sys.version_info < (3, 5, 2):
+                    del self
                 raise ValueError
 
         t = T()
+        refcount = sys.getrefcount(t)
+
         if method == "function":
             pytest.raises(ValueError, t)
         else:
@@ -175,14 +181,7 @@ class TestRaises:
         # ensure both forms of pytest.raises don't leave exceptions in sys.exc_info()
         assert sys.exc_info() == (None, None, None)
 
-        del t
-        # Make sure this does get updated in locals dict
-        # otherwise it could keep a reference
-        locals()
-
-        # ensure the t instance is not stuck in a cyclic reference
-        for o in gc.get_objects():
-            assert type(o) is not T
+        assert sys.getrefcount(t) == refcount
 
     def test_raises_match(self):
         msg = r"with base \d+"